Topic Horde side guilds....
I think we're the only Horde-side 25 man guild remaining. And we're still working on progressing through Firelands HMs. Since we only raid 2 nights a week, I wouldn't call us a hard core guild by any means.
Personally I think the biggest problems with 25-man is the AFK boss. Nothing like getting all set up and buffed to pull the boss when someone isn't responding. Since we're comprised of mostly adults with wives / kids, there's someone getting harassed about every 30-45 minutes and gives the "I need a sec" line. Which then turns out to be 3-5 mins...
Some of the fights are more forgiving in 25-man. Some are not. Rhyolith can be done with as few as 20 in Hard Mode if you have decent folks. If you start losing folks in Alysrazor 25HM or Baelroc 25HM, then you're going to start having adds not dying in time (Alys) or a really dicey Torment rotation (Baelroc). And I think we have a different person either crash or DC every other fight.
I think between AFKs & DCs, 25-mans are harder (or more annoying, take your pick) because they are 2.5 times likely to happen. Getting 10 folks with lag-free, stable connections is a godsend and why I think most folks prefer that tier or raiding.
I think its a matter of perspective. When I was alliance I did ten mans. Then the guild pretty much fell apart and I moved to horde, found Nephandi willing to give me a shot. I remember my first few nights raiding 25 for the first time I thought it was so hard and 10 was so much easier. Then I got acclimated and find 25 to be just as easy as 10 man. Barring a few fights here and there that are simpler on 10 (domo specifically) but not by so much to make it a radical difference. Other fights are easier on 25 (beth (to me at least)) so it evens out in m opinion.
In my opinion it boils down to this: 10 man difficulty lies in personal responsibility since 1 death has a much larger impact than in 25 while in 25 you have to wrangle 24 other people of varying skill level.
I'm just a decent, in my opinion, resto shaman though so meh. Comes down to personal preferance really.