This is based on purely anecdotal evidence based on my experiences in spheres of DW fandom, so no doubt there will be people go go against my theory, but basically I would group fans by and large in one of two categories: ‘2 5 10 fans’ and ‘3 8 12’ fans. Obviously, there is overlap and picking a true top three Doctors is impossible, but what I tend to notice is that people gravitate towards being a fan of 5s era or a fan of 3s.
This isn’t to say it’s a battle lines being drawn kind of split - I myself am a 3 8 12 person but I am partial to a bit of 5 now and again. It’s just like they are two quite distinctly flavoured era of the show with certain traits of Doctor characterisation and companions and types of stories etc. It’s not that deep as a theory and doesn’t even mean anything really, I just find it interesting how people’s favourites tend to cluster.
I also made a poll about this ages ago and I never did anything with that data 