robert53-
I demoed the Ultra deck with the MM cart, in my system. Nice table for the price point.
The only Rega experience I've had is years ago, I had a P5. Rega has updated their line since then, so can't comment directly to your question.
The Mofi however, is well built and made in the USA. The MM option is average, but may fit the bill for someone who isn't too demanding of their record playback requirements. In you go that route, it's a plug and play deck. A decent MC instead,would be a game changer IMO.
Are you using the best phonostage you can afford? You will get more out of the table you decide to buy.