Kid Icarus Uprising, the Pokemon games, Fire Emblem, Yoshi, Pushmo, Dillon's rolling Western, Starfox 64 3D, the handheld Mario, Zelda, Metroid, Donkey Kong etc games etc etc there is plenty of source materials Sakurai can choose to make for some great stages for the 3DS version. The Handheld consoles have had many great games that have yet to be represented as stages in Smash, it will have plenty of source materials for stages and music to work with. If you are worried of a tiny screen size then I'd advice you to purchase the 3DS XL.
I believe the reason we get more Wii U screenshots isn't because of bias for the Wii U version, but because Sakurai uploads these screenshots on Miiverse first in the Super Smash Bros section, so obviously most of the people who get to see those screenshots first are Wii U owners so it makes sense to advertise the Wii U version more in that. Once the 3DS gets its own Miiverse released I'm certain we will get to see more 3DS screenshots as well. I do agree on the lack of 3DS Villager and Wii Fit Trainerpictures though, then again, they are running a little behind on schedule on the 3DS version so I guess they aren't fully ready yet to reveal these two characters for the 3DS version at this point of time.
Oh yeah, Sakurai also said recently that the 3DS screenshots don't do the 3DS version justice as you really need to see the game itself in motion in order to appreciate it, which I can understand where he is coming from since many 3DS games really don't look as good in screenshots than that they actually are if you were actually playing them on the handheld itself. That's possibly another reason why we don't see as many 3DS screenshots, Sakurai likely feels that they don't really do the 3DS version justice. It's one of those "Seeing is believing" type of things.
Remember, bigger doesn't always equal better, New Pork City is as big of a stage as you can get and its one of the least popular stages in Brawl and its mostly because of how large it is. Besides we haven't even seen all the stages yet so we can't tell yet if there are larger stages, so far the Reset Bomb Forest looks like quite the decently big stage seeing how there is a section cut (from what I can tell). Besides, if screen size is such an issue for you then like I said, purchase the 3DS XL then. Plus we haven't even seen all these stages in motion so we can't tell how it will be like in the 3DS.
Honestly, the stages in the 3DS version look about right in terms of size, how big do you want them to be? :/
As for the Circle Pad, that's not really the game's fault but the handheld console itself. I don't really see the issue in it but oh well.
I wouldn't worry too much about it if I can be totally honest. The 3DS version will be just fine. It won't have another SSE to worry about so all this unnecessary memory hogging clutter will be gone thus there will be more space that they can use for more important things such as the game's balance and any other modes and features they can work into the game. I highly doubt Sakurai will purposely make the 3DS version an inferior game, he will most definitely pour as much energy into the 3DS version as he does for the Wii U version and push it to its very limits that the system can handle. I mean just look at Kid Icarus Uprising for crying out loud.