Prima's will almost certainly offer more bass, due to the subwoofer. They won't sound as good though. One reason is the Prisma's are cheaper. There are more materials and components involved. That means the more components there are, the more the budget is stretched between them. Also larger woofers produce a better more balanced sound quality, when compared to 2.1 speaker with two smallish satellites and a subwoofer.
It depends I suppose what you are going to use them for, primarily. If you are after plenty of bass for gaming, maybe the Prisma's or other 2.1 speakers will be a good choice. If you are after overall sound quality for music, then no doubt the 1900's are the better choice.