There have been several polls on that, you can use the "advanced search" function.
The trends were not that clear : there are all kinds of tastes actually.
Anyway, people who just spend time lurking the forum won't have a proper opinion as it's often the same ones who talk a lot (myself included) and give the impression that they are numerous and represent a lot of people
, which is just wrong. Also the ones who spend a lot of time on this forum are often trolls and also often are full of themselves. You will have a bad opinion of every fanbase if you just read what these posters post. I've often read this wrong interpretation on this forum that the most talkative posters on MTF truly represent their fanbase, which is 100% (well 99%) wrong.
People in real life are very different, and you can already see that in other forums.
Fedfans usually don't like Nadal, that's the only very obvious trend, for various reasons of course there's the "losing" factor, but not only Fed and Nadal are opposite in many aspects. Usually Nadalfans think that Fedfans just hate Nadal because Fed loses to him, because that's the most acceptable opinion for them : it's hard for them to imagine that one can't like Nadal for other reasons.
Among Nadalfans, it's not visible on this forum but many ones like Fed or at least respect him at least from what I read on multiple forums. I was nicely surprised by that. I guess defeating him helped, the fact that Nadal praised Fed a lot also helped ... and of course that there are many reasons to respect Fed and it's visible in the whole tennis community
. Also I was pleasantly surprised that many Nadalfans really are humble people, although on this forum you will not realize that at all
I have the impression that more Djokofans don't like Fed than Nadalfans dislike Fed, anyway I've often seen they had a strange and peculiar relationship to Fed, very much concerned about him even when Nadal clearly was Djokovic's main opponent. I think Tignor was on something when he spoke of a "Fedipal" complex about Djokovic, remember "the king is dead, long live the king" ?
About Djokofans disliking Fed, there also seems to be a specific "nationality" factor : I think the Serbian media played a lot on that competition with Fed, and also some liked to give a bad opinion about Fed for that reason.
Of course, disliking Fed, or, specifically on this forum, disliking visible Fedfans, has also been a reason to cheer for Djokovic or for Nadal for some, at different periods though. Also some who were disappointed by Fed when he declined also went on to cheer for Djokovic, as he's the one who's most "offensive/complete" out of the other top-4, or at least out of the top-3 because these ones were rather gloryhunters, and it was hard for them to cheer for the slamless Murray
Besides, specifically on this forum, an artificial "association of interests" has been made between Nadal and Djokofans, because of the high number of Fedfans. I've not seen it anywhere else.
Personally Fed is my favorite, and I'm allergic to Nadal, between Djokovic and Murray it depends, I prefer Djokovic's attitude and desire to create more, also his personality, but I admire Murray's talent, esp. since I saw him live. Also I prefer Fed-Murray's match-up than Fed-Djoko's, more interesting matches imo.