Both are excellent games with some notable differences. Whether you should do both is entirely up to you, how much time you can spare and how into the games you get. If you have the time and get into it, you're robbing yourself of 10 hours of good gameplay if you skip 1. If not, 2 is the better game.I'm assuming you've played the first one? I'm about 1/4 through it and am wondering if I should just skip to the Grimrock 2, or is the first one is still worth playing? I mean, I know it's good, but should I spend that time just playing Grimrock 2 instead, is what I mean. In your opinion, of course.
The big difference, of course, is that 1 takes place in one large dungeon while 2 is in a more open world with small dungeons scattered throughout. 2 is also harder.