I would get Tiny first but something is too be said about Ultra Tiny.
Ultra Tiny is so small I keep it comfortably and permanently in my bag. It's the "biggest" game the size of a deck of cards that I know of and it's very charming.
I personally think the UTEK version is still comfortable to play. There are big box games that are more fiddly than that. Plenty of games where you have to track stuff with small cubes like those in UTEK.
In terms of functionality TEK is better. It has those exploration tokens, and is compatible with the expansion.
UTEK has solo rules but you need to bring your own die and you'll probably don't play it a lot solo anyway. Still the biggest feature of UTEK, that doesn't need to be underestimated, is that it's a game you can literally bring everywhere.
They say that "The best knife is the knife you have on you". Well the same is kinda true for boardgames as well. The best boardgame is the one you have with you. Most of the time you plan to play boardgames ahead of time but every once in a while a opportunity arises to play a game when you weren't prepared and then you're glad you have UTEK in your bag.