25 is a better fit for LFR, most of the reasons have already been said on previous posts.
I’m more curious as to why would someone prefer 10-man over 25 in LFR?
If it’s because of performance issues then that’s a totally valid point, but other than that, I can’t see it, except for simple personal "abstract" preference, which is also fair but hard to use as an argument to try to convince devs to spend resources on creating one more difficulty level and adjust/balance LFR for 10man when 25 works just fine. It feels a bit redundant to me.

10man would probably cause higher queues and be less forgiving when raiding with inexperienced players as they would have less “backups” in the same role.

10mans are great when you have a coordinated group. It’s much easier to organize and coordinate 10 people than 25, so it makes a lot of sense for normal/heroics where someone actually has to create a raid by gathering a group of skilled players and still lead them.

But LFR doesn't require much coordination, and the group is automatically generated, so what would the advantages of 10man be? I’ve seen this suggestion before, so I’m really curious about it and not trying to be sarcastic here, maybe someone has a logical argument that I’m just not thinking about.

09/01/2013 15:41Posted by Lirena

A lot of people like 10 mans over 25s for the same reason they might like purple and can't stand green. It's just their favourite. It could be because 10s are quieter and cleaner (my preference), because people are more accountable, because there's more of a chance for an individual to shine etc. etc.

That's the kind of answer that I was looking for, when I said abstract, I meant it in a way where you can’t build a logical argument, sometimes you just like something without rationalizing about the reasoning behind it.

When you say “I like purple and can’t stand green” that’s abstract. The only way you can convince someone to adapt the world around that idea is if there’s so many people wanting the same colour that it simply doesn’t matter why they want that colour, numbers matter.

What I was looking for was actually this “10s are quieter and cleaner; people are more accountable; there's more of a chance for an individual to shine”. That’s not abstract, that’s perfectly logical and a good argument, so thanks ;)

09/01/2013 16:11Posted by Sanaëe

From my experience, healing in a 10-man and in a 25-man settings are really different : you're far more likely to use single-target healing and triage in a 10-man while in a 25-man (especially in a less organized settings like LFR), you'll use far more aoe healing.

That’s true, play styles do change from 25 to 10 man. But I believe that’s something that affects healers the most since you have a fixed number of players that you have to heal. Tanks and damage dealers will probably only slightly change their play style due to bigger aoe packs, which is not constant and affects mostly trash mobs. Still, a valid point and a good argument!