The developer of PRIMA here.

If you use method "cobyla" from scipy.optimize.minimize, then answer is now. PRIMA already performs far better (in terms of the number of function evaluations). See the comparison at https://github.com/libprima/prima#improvements .

The bugs are indeed only a secondary reason: they can only be triggered under special situations. They may not affect your usage at all (when it does affect you, the consequence is catastrophophic).

They claim there are bugs in the COBYLA solver implementations included in scipy that this implementation has fixed. So I guess if you run into any of those bugs then PRIMA is better.

They're apparently also in discussion with the scipy team to include their implementation in scipy, so hopefully the question will be moot in the not too distant future