I just read an excellent post over at Sacred Duty, link, and while it did consider all of the available data it did have some assumptions. The assumption of equal skill, the assumption of time spent, so forth and so on. Can't fault him for that because in most cases like this we can only go with assumptions. It is a great read and I suggest it for those that are interested in this type of stuff.
I would like to make some assumptions myself on the topic.
My personal opinion on the matter is that any of the 25 man guilds would have done the same with 10 man as paragon did and not because 10 mans are easier but because of the simple fact that they have more skilled members ready to go.
Given that serious raiders will have their main and perhaps even three or four alts geared up means that there is always the option of class stacking, should it be needed for any fight. However, even considering skill, some people are better at some things than others are.
Lets say for example an affliction warlock is extremely powerful on a fight and you have a 10 man guild where three people have raid ready alts they can bring in that fit that spec for the fight. So you will, of course, do so to speed progression would you not? Those three, because that class and spec are great for the fight, will be in the mix regardless of their own ability to play the class as you know they will still do well as they are great players.
Now if you just happened to have been a 25 man guild that just went down to a 10 man guild you might have 7 or 8 people that have raid ready warlocks. If you switched to 10 man, like paragon has, you could easily fill all the DPS roles with just affliction warlocks and even have the benefit of being able to chose the 5 best ones and not just the only three you had if you were a strict 10 man before hand. Like I said, skilled players might be skilled but there are always some that will be better at certain things than others. So now you have the option to take the best 5.
This is one of the reasons I believe paragon had the larger lead over other 10 mans, as mentioned in his post, that is being used as a reason to think 10 mans are easier. They were coming from a 25 man into a 10 man and as such it might leave them with a few more options than the average 10 man guild that has always been a 10 man guild has. Choosing the best 5 locks out of 7 will of course leaves you with a better 10 man team than just taking the only three locks you have regardless of how well they play the class, don't you think?
Again, I am making my own assumptions. My assumptions here are that they still have a lot of extremely skilled players hanging around that have not left for a 25 man guild yet or were hoping to squeeze in and/or were willing to wait for a second clear to remain part of a world first guild.
If my assumption is true, which we can never know for sure, this means that on any given fight they have the ability to better adapt or stack or adjust on an encounter by encounter basis than any other 10 man that had always been a 10 man would have. This the reason for the huge gap between them and the second closest 10 man. They had a larger pool of skilled players to choose from.
I do believe that if any of the 25 man guilds did progression as a 10 man team they would have seen it move along faster as well for the exact reason I mentioned above. The ability to pick and choose the best of the best of a stable of exceptionally skilled players and choose which classes to use on an encounter by encounter basis undeniably gives you a huge advantage when you are trying to get things done first.
Paragon did not finish first because 10 mans are easier, they finished first because they had more tools available to them to do so. That is my assumption and if my assumption is true that throws all the data out of the window because you can not compare a 10 man to another 10 man when one 10 man has basically almost a 25 man raid teams worth of exceptional players at their disposal and the other doesn't.
That is just assumption one. Assumption two is the history of 25 mans being where the action is and where the world first race is. It has been that way as far as I can remember but do not take my word for it, take the word of anyone that has been around, 25 is where the action is.
This is assumption number two. The best of the best, or at least the ones that attempt to be the best as it means something to them, all join 25 man guilds. This means there are not that many hanging around in 10 mans waiting to be subbed in if needed. The majority of the better players will be in 25 man guilds to begin with. Not to mention many really great players that could be in 10 mans are sitting on the sidelines in 25 mans just for the chance to get into the group and be on a world first team.
This does not mean there are not any skilled players in 10 man guilds because saying that would be a flat out lie. It is just saying that the ones whom world first and progression matter to most usually gravitate to a 25 man guild. This is why, in part, you see so many 25 man guilds finishing before 10 man guilds, they attract the better more serious players based on history.
This is another reason for the gap between #1 and #2 in 10 mans. It has nothing to do with 10 mans being easier and it has everything to do with the majority of people that world first matters too are in 25 man guilds.
So what does all this have to do with 10 vs 25 man difficulty? Not much really. People are just putting paragon down because they are 10 man saying it doesn't count and I think that is wrong. First is first and any of the 25 man guilds that wanted world first could have done the exact same thing paragon did and ran it 10 man if they thought it was easier and they thought it would get them worlds first.
I have always stood by the belief that there is a reason all world first guilds are 25 man, at least since cataclysm came out as before that 25 was without doubt the one that mattered most. The reason, since cataclysm, why 25 man guilds are always worlds first is because 25 mans are easier. It is as simple as that.
Look at all the cheating that has gone on over the years that people got caught and didn't get caught with? Every single one of these world first guilds takes any advantage they can to become worlds first. They will cheat and hope they do not get caught, they will game the system every chance they get, they will class stack to take advantage of something that went unnoticed.
Lets face it people, if 10 mans were easier they would be doing 10 mans because first is first and that is all that matters. People that will lie, steal and cheat to be world first would not stick to their guns and play 25 man raids if 10 mans were easier. If 10s were easier they would do it to get world first, just like they would abuse a mechanic or cheat in an effort to be world first.
Now that is my final assumption, the assumption that any guild that wants to be world first will always take the easiest route to accomplish it. We have seen it. Maybe it is true, maybe 10 mans are now easier and maybe paragon was just the first one to notice it. Unless all guilds do it in the same format we will just have to live with world first over all, world first 10 and world first 25.
So lets ask the question that begs to be asked. If 10s are really easier why are more competitive groups not moving to doing 10 mans just to win?
The true test will be if paragon keeps getting worlds firsts when they do not have as much depth as they did right now changing from a 25 down to a 10. Can they still remain number one? Only time will tell. Will more guilds follow suit? Only time will tell. As far as I am concerned, whichever format most guilds are playing on is the easier one because like I said, people that want to be #1 will do anything to get there and that means following the path of the least resistance.
In the end this is what it comes down to...
If you are a 10 man raider, 10s are harder.
If you are a 25 man raider, 25s are harder.
The grass is always greener on the other side my friends.