If you really want to improve your live recordings, a step up from those Soundmans, or any other mini mics in the world, is the DPA 406xs. Best mini mics in the world, hands down. You won't be sorry if you nab a pair. Upgrading those mics is way more important than a pre or a/d, especially one that you can't stealth.
I can't comment on the studio use of a Mini-Me or UA-5, but a primary feature of both is portability.