A big, huge asset to Marvel United is that it plays as a quick, modular, and asymmetrical super hero puzzle. You can and will chain multiple games with multiple setups in less than 2 hours. This also makes it its biggest weakness as the game demands a bit of a collection to feed the modular elements.
As to collection, Marvel United X-Men and Marvel United are the same game. So I’d suggest looking at both and mix at will. In addition to the combo you listed, there should be X-men core at least readily available.
Which are good? Sorry, I like them all as the each add vital variety and twists (heroes and villains). X-men is new so they got comfortable with the design and it’s a bit more fleshed out IMO, but also not MCU focused unfortunately. Villains add the biggest change of flavor.
Random thoughts:
—Dr Strange is a really unique hero from the KS exclusive box. He is a heck of a pick up in that combo.
—Thanos expansion does a neat campaign that ties into the movies while also giving a lot of villains for one off play.
—X-men Sentinel box (Days of Future Past) is really cool. I add them to basically every game as a modifier. VERY COOL set. It’s a crime it’s KS exclusive.
—Sinister six is kinda neat.
—Spideman box has cool heroes, but the mode (secret identity) is meh.
—I think I liked Guardians box. I’ve played Groot and Racoon a few times.
—Deadpool box is meh.
—X-men heroes have at least 4 unique cards per hero deck while MU usually has 3 (but they all have unique symbol make up out of the 12). Thus MU is a bit more subtle as Capt. America has more Heroic symbols than other decks. X-men have that and one more unique card per deck (at least one more). Some of X-men heroes have cards that stay in effect or start in play or whatever. The design grew after MU.
Um, I struggle to think of specifics. I like Red Skulls’ mechanic, but he is a bit easy. I don’t like Taskmaster’s gimmick. Really, I think playing 1 or 2 heroes against the same few villains would be doing it wrong. Puzzle modularity is amazing here and it sucks that it’s a CMON KS game for that reason. You don’t need it all though. Just more than a core for sure.
TLDR advice, get that combo plus the X-men core set at a minimum. If you stop there, it may go from engaging to stale in a few sessions. Or fail to gain momentum. If you like it, accept the minor up price on a few cheaper ($50) expansions based on favorite heroes and get what you can. Sentinels are really fun. The round neoprene map is useful bling. If for whatever reason you can snag a KS stretch goals box, they each have tons of variety in themselves.
I bought my MU with full “EBay tax.” I was in X-men KS. My MU collection cost me a lot and it’s one of my favorite finds. I doubt I would have liked it, if not hated it, off of just the core box. Variety is critical here.
