Usual list of differences:
1. Wider ROPs, to make room for the turn around seat
2. Turn around seat so you can use the backhoe (much better than a 3ph backhoe without turnaround seat - as the backhoe sits much closer to the machine, so better departure angle when loading onto a trailer)
3. Subframe that the backhoe attaches to. The BX frame isn't super strong, they decided that it needed reinforcing for a backhoe. The BX23s has that reinforcing, I believe it reaches most of the way along the chassis
4. No 3PH equipment. The hydraulics are there, the arms and top link aren't, you can option them
5. I think the loader is slightly different, but not enough different to care I believe
I think they're actually identical horsepower, they're in the middle of rerating their machines so the horsepower they used to claim is no longer the horsepower they claim. You may have two different sources of info, one before the HP change and one after. I'm pretty sure it's an identical engine.