difference between 10 and 25?

[Ranikotar]

Raid comp is important in 10mans. If you bring no interrupters to Halfus/Council/Cho'gall/Omnitron/Maloriak/Nefarian you are asking to wipe, etc. In heroic progression sometimes having an off healer helps (read: Shadow Priest).

The basic differences are as follows:
1. 3 tanks (25) vs 2 tanks (10): Makes the biggest difference in Halfus Heoric and Nefarian (both normal and heroic). Might make Chimaeron heroic easier as well.
2. Margin for error: As what the posters above have mentioned. 25mans have bigger margins for error.
3. More class options: If you have a naturally good mix you never have comp issues in 25s.
4. Less movement space: Room sizes are similar both 10 and 25. 10s have more room to maneuver
5. MISC Stuff: 10s are usually easier to organize and ensure everyone is doing their jobs well. The bigger the raid the more complex it is to lead and monitor performance.

This.

Al'akir fits #4 very well. In 25 you have very limited room to move in p1 to avoid the tornadoes (not that it's hard). In 10 you can spread out and have a whole lot more room to maneuver around the random crap that happens. The Ascendant Council is another example of this. In 10 man you have fewer people eating the lighting discharge thing while in 25 you have multiple people chaining it.

Atramedes is a good example of #2. In 10 I'm pretty sure with only 4-5 people alive you're gonna end up hitting the soft enrage (Zero gongs left) if everyone died early on. In 25 he can easily be 10-14manned for a good 50-60% of the fight (Yes i know that's absolutely horrible).

It will hurt your raid a lot more trying to carry a few sub par players in 10man than 25 also.

This is all regular to. Haven't started up heroics yet.

[Brett Skullcrack]

Since you're doing normal modes, the only difference is Nefarian really. In 10 man you can use a frost mage to control the adds, but in 25 man there's too many of them and you really need a tank to do it.

Since your two 10 man teams probably have two tanks each, I'd pick two of them to be main tanks with dps offspecs for the fights where you need only one tank, and two of them to go dps main specs with tank off specs for fights that require more than two tanks.

[reflection]

You don't have kind of like 1000 CDs in 10 man

[Sentreenay]

Full paladin raid is cooler, since they can actually do all the 3 roles

wrong palys cant do range properly :P (some messed up holy exo-spam for range would be jokes)
full druid run can do everything though

OT:
10 is harder as if you dont get the corect class combination you wont go far or it will be harder than it should be, e.g not having a DK, Hunter and paladin can make it hell >.> and if you lose 1 or 2 people that tends to be it be thay a healer or dps or tank its normaly game over, evan with there being more space that means you have a higher risk of geting out of range of a heal aspecily the the case of a shamy chain heal not being able to hit all 3 (4 glyphed) targets can realy mess up there healing abiity.
with 25 the difcalty is spacing and organising not to much elce as long as you have the 3 tanks and 5 healers, your also prity safe with mana as you have a lot more mana regen available, and you can alow for a few dps dieing off without causing you to run low on dps befor the enrage and such, allso with the 5 healers or 6 as some take thats gona mean a lot more heals going out to those that need it faster.

[Yoijimbo]

Actually, 10 mans are not really much harder than 25 mans... 10 mans are easier to control and everyone learns the base mechanics faster. The bad stuff is that when one of your core raiding group has to be away for one night, it's really hard to find as good as the player who had to be away. The playing style is different and the same group learns to play with each other after a lot of weeks and wipes...

I prefer 25 mans, they just are more fun and exiting with its full chaos and rage. :3

+ There is an optimal 10 man group for all necessary buffs and stuff. I haven't checked the latest situation after 4.0.6 buffs and nerfs, but some tanks, healers and DPS are just more useful in 10 man raids than others. (Well tbh, healers are pretty well balanced in this patch)