Grounded wins hands down. Smallland's quests are very simple. The dungeon design is ok in Smallland, but not nearly as good as Grounded. It is nice to be able to relocate your base in Smallland if you build in one of the right trees though. Cuts down on travel time.

I've played both. Smallland is jankier, but supports more than 4 players. Boss fights in Smallland are easier.

The gliding in Smallland is pretty nice.

That's my favorite esoteric programming language!