Which of these two anime should I watch next?

Kobato is way better in terms of storytelling. It's exactly what you would expect of something written by CLAMP (if you've seen Tsubasa Chronicles, xxxHolic, or Cardcaptor Sakura). There's the same multiverse theme going on here with a few emotional moments. The plot twists may or may not be unexpected, but they're enjoyable. But while not completely absent of romance, it is somewhat lacking in that category...until, of course, the end.

Bokura is told in a typical shounen romance fashion. There's really nothing new. Same old love at first sight crap and deus ex machina setups. Spineless protagonist who can't confess and dandere heroine. The plot is just totally predictable. I mean, it's not bad, but just don't expect anything new.

If you like a good story, go with Kobato. If you like a good romance, go with Bokura.

I havent seen either but from reading what they are about I would start with Bokura wa Minna Kawaisou