Hi. I'm new to the community, and I hope to have a nice time debating and sharing laughs every now and then.
I'll do my best to tackle the issues on hand: Should the Wii U have more chars than 3DS? Are Wii U users entitled to such a difference? I'll speak from my perspective, having a 2DS and no intention to get a Wii U. But let's start with the Pokemon analogy, in which I believe you're omitting information.
When talking about ames in the same generation, no Pokemon game has exclusive Pokemon. You can catch X on version A, and Y in version B. And you can trade one for the other. Ta-da! Your use of 'exclusive' is incorrect here, as you're proposing that Wii U version has characters that can be played in that version and that version only. Therefore, you used a bad example that has nothing to do with the topic at hand. And I can understand it: you want more characters because you pay more. Okay, but then...
Should the WiiU version have more characters than its portable counterpart?
Yes and no. Most people being hurt about the little differences between 3DS and Wii U versions seem to be thinking in terms of having already paid for the game (which they haven't) without knowing about them (again, it's not the case). I'll tell you a secret: Nobody's forcing you to buy the Wii U version. If you don't think it's worth the price, don't buy it. That's how markets work. I understand my argument can be disputed ("But I don't have a 3DS, so I have no little choice!"). But if you had a Wii U AND a 3DS and were still going to buy the game, there's no point in arguing over this. Still, as I reckon the Ice Climbers had to be at least partially developed (how else would they know they're hard to implement?), they could have gone the full way and included them at least in the Wii U version. This is the only kind of extra PJ's Wii U should have. Let's remember this is Smash 4 we're talking about, there's (on paper at least) no reason for one to be inferior.
Also, there are probably lots of extra modes for the Wii U to be unveiled after the 3DS release.
Are Wii U users entitled to more content?
HAHAHAHAHAH. Again, just because you'll pay more it doesn't mean anything to the content you should get. If you're not being lied to, you're free to choose. Plus, 3DS and variants amount for a higher quantity of sale figures than Wii U's, and by means of inferring we deduce that so will their respective versions of Super Smash Bros. (although the latter will get an important push with this release). Alienating most of your potential buyers is NOT a good strategy.
TL,DR: No point in having more chars in one version than the other (Climbers excluded), I wouldn't mind them getting a couple extra modes though.