In my opinion both are very fun for very different reasons. 3.5 (as many have said before, you should really grab pathfinder if going this root) is fun because the classes are VERY different. Many have spells, which are varied between classes. It is also a lot less board dependent. My personal problem with Pathfinder (and 3.5) is that the ranger doesn't seem to fit anywhere, and I love the ranger so that disappoints me. (note: I love pathfinder by the way having begun playing 3.5 a few years ago, meaning I am quite green in the d&d department)
4e is what I am running a campaign in now and honestly I am loving it and so are my players (they are all d&d virgins in fact) what I like about it is the ease with which you can set up encounters, I like the consolidated skills, and I like that they weren't afraid to give the players power. I really dislike when you come across a spell or magic item that sounds fantastic, world changing even and it gives you a +1 or +2, it just feels like math not a living world (and that is an issue that all editions encounter to be honest).
I'm not sure how to describe it but it seems that with 4e they weren't afraid of breaking with status quo, you don't have to play one of the typical "like an human but," races and there exist races that can teleport or speak through their minds at lvl 1!
In closing it may be that I am rather unbiased due to my lack of experience with the franchise (I usually prefer white wolf to be completely honest) but one has better combat but is more constrained and the other has better flavor but a lot more rules.
4e is what I am running a campaign in now and honestly I am loving it and so are my players (they are all d&d virgins in fact) what I like about it is the ease with which you can set up encounters, I like the consolidated skills, and I like that they weren't afraid to give the players power. I really dislike when you come across a spell or magic item that sounds fantastic, world changing even and it gives you a +1 or +2, it just feels like math not a living world (and that is an issue that all editions encounter to be honest).
I'm not sure how to describe it but it seems that with 4e they weren't afraid of breaking with status quo, you don't have to play one of the typical "like an human but," races and there exist races that can teleport or speak through their minds at lvl 1!
In closing it may be that I am rather unbiased due to my lack of experience with the franchise (I usually prefer white wolf to be completely honest) but one has better combat but is more constrained and the other has better flavor but a lot more rules.