CNET did a nice comparison of the two. In my opinion, for most people I would recommend getting the Bike+. Peloton seems to have worked through most of the quality issues they had at launch and the newer hardware is likely to last longer and work better as they add new features.
I'm still using the old one for now but expect to upgrade before too long. One thing I am expecting is that my output will be lower once I make the switch.
We explore if the Peloton Bike Plus is worth the extra cash.