Supposedly, the B1.2 is an upgrade optically over the B1. What made maven famous was their awesome B2 line and the C series of entry level binoculars. Each of those, because of Maven's cost structure (direct to consumer) compares nicely with binoculars that cost between 50 and 100% more. This is Maven's goal across all their lines.
HOWEVER, the one that is most often known to have lackluster performance is the original B1. It's the main one you hear people talking about that doesn't meet expectations. They're not bad, but they don't punch above their price point like everything else Maven builds. If you have $1000 binos already, you won't be upgrading. If you are running more entry level optics, you'll end up with an upgrade. But for the same money, you'd be much happier with the B2's.
Supposedly, the new B1.2's fix this disappointing performance supposedly, but I haven't seen much on them since they came out. Whenever we talk high dollar Maven, it's still the B2 that dominates conversations.
EDIT: In response to your question if it's a worthwhile trade, I would say you'd be getting the short end of the stick, especially if you already have a decent pair of binos. I wouldn't entertain the trade if it was me, but I'm just some random guy on the internet.