No, it's not very much like SPAZ at all. For one thing, Weird Worlds is much faster paced and not so expansive. A single game of Weird Worlds can be played through in 10 to 30 minutes (depending on the size option at the start of the game and on how many battles you take on when you're evenly matched or outmatched and thus have to play more carefully). Emphasis on an almost-arcade feel and on replay enjoyability.
It's kinda like the difference between watching a 15-inning baseball game and watching the one-minute highlight reel.
(Not to put down SPAZ, which I got with a Humble Bundle but haven't yet done more with than play through the tutorial; I'm sure it's got its own merits. Sticking around for a long baseball game probably has its merits too, especially to baseball aficionados. But the highlight reel can appeal to a wider audience, can fit into your schedule, and can be kinda addicting.)