The Praxis conversion BB and the Wheels Mfg. adapter are different approaches to allowing the use of 24mm spindles with BB30 BB shells. The Wheels is a true adapter that works with the existing BB30 bearing to step down to a 24mm spindle opening. The Praxis is a complete bottom bracket with external bearings.

I use the Praxis conversion BB on my Allez (needed to use a 24mm spindle PM). I chose the Praxis, because it seems like a well integrated solution rather than an adapter.

I've put a couple thousand miles on it, so far, and it works well.