I plan on getting both - while my budget doesn't cater to collect all the characters from both games, I can always do that over a longer period of time.
The thing is about them is Infinity will always offer more in terms of replayability. While the ToyBox is lack luster as there is "no point" in it (What do we achieve? Yes, we can make our own worlds and challenges but what is the goal? Unless we can make missions/quests and storylines using NPCs and what notfor other people to experience and we can experience ourselves then yes). There is still more replayability here.
In Skylanders you can only replay it so much until it gets repeatative and I'll tell you now that the amount of characters per game they release - there isn't enough content without it getting repeatative to level them up, no way at all.
If Skylanders wants to "beat" DI then they need to think (as some have said in this thread) their strategy for long term replayability. I love the characters and character designs, the personality and life that they put into each and every one of them (Which DI doesn't need to do completely as they have stories and backgrounds for each already made set in their own universes) but to complete the experience they need something.. more? They could do this in a variety of different ways:
-Make a Skylanders "Free-Roam" mode in a sense (kind of like the lego games where they have the levels - so skylanders would keep their own type of game and then a freeroam type of area). They could add RPG elements and even side stories on top of this (heck, each character has a backstory, why not be able to play those backstories as flashbacks?).
-Copy Toybox and make a "create your own" area within the game.
-Minigames that allow you to do "something" somewhat like the old online world.
-Probably more reasons, but I'm not that imaginative.
DI2.0 seems more interesting to me than Trap Team (Hope there is a mute button on that new portal...) and that is only because of the replayability aspect. I love being able to get more content out of the games I play. (Just runnng arond is fun) but on set narative story lines which make you go from Start to End will always get repeatative.
I do hope when Skylanders 5 releases (or heck, if they start edging some of it into Trap Team) there will be replayability for the amount of characters there are avaliable.
Good luck to both games anyway
(Also, DI2.0 while they are aiming for the Marvel Audiences right now they also have Disney characters in it - Maleificent, Stitch and the girl from Brave have been confirmed - not offically, but hinted at by staff in previews of the game from the main trailer so there is still hope).