They're basically Nocturne, only easier and with a more traditional story and without demon fusing. Instead, you buy spots on a grid. Both games also feel more linear.
I made it some ways through Digital Devil Saga 2 before getting fed up with the fucking story. I thought it got pretty dumb and the dialog was just completely stiff and wooden. Mechanically, though, both games are pretty great and well worth a shot if you like the combat in SMT games.
The dialogue being stiff and wooden is, well, part of the story (also ofc the story is pretty dumb, that's part of it's charm!)