Never used a UA-5, just a UA-30.
I have used an MMP-2 for a few shows. Yes, you need AC (or some complex DIY battery concoction). If you have AC, its fantastic:
Mic pres, phantom power, 24/96 conversion, multiband eq, compressor/limiter, pro connectivity options (but not USB), and good meters all for under $200.
Where else can you get all that?
You also get the modelling features, although I don't really care about them and don't use them.
Build quality is good.
Sound is good.