Think there will be more on the PC servers for sure ..... not saying that the console servers will be empty though
PCs will most likely have the largest playerbase. But i just say play whatever you feel most comfortable playing.
Entirely up to you. You will have a slightly harder time with text chatting because of the nature of using a virtual keyboard, however the touchpad is being utilized for a faster, easier experience.
The only assumed downside you will have with it on PS4 will be lack of LUA support for UI mods. I think we can assume any mods won't be available on consoles because of red tape although it's no means impossible; Unreal Tournament 3 for PS3 for example.
It's quite hard to say how many players will be playing on PS4 that on PC but I'd expect a overall bigger playerbase on PC in the long term.
There are some very nice PS3 controllers that have a mini keyboard attached to them. Most likely the PS4 will have similar controllers.
I plan on getting it for PS4. I've always been more comfortable with a controller.
I'm actually considering buying the game on both PC and Console. PS4 for solo questing, PC for PvP and PvE raids and all that.
I'm not sure what the differences in graphics will be, but the developers have said that the PS4 and XBOX One are both well above their min specs for PCs. So you'll probably be playing on the equivalent of medium settings or so.
If controllers are your main worry though, you should know that you can use a controller with PC games. Even though ESO doesn't currently have native controller support for PC (which is odd because they've gotta make the control scheme for consoles anyway) you can use 3rd party software like XPADDER to make the controller compatible. Its actually really easy.
I think the experience will be good on both. In my opinion, PC will have a slight edge because of community. At the same time though, if you don't already have a gaming PC, you'll be spending a lot more than you would on PS4. There is no way you could build a gaming PC for the same price as a PS4 and have it be equivalent.