10 years ago, you couldn't have given me an MM bass. I was playing Fender, Status and F.bass at the time.
About 5 years ago, I bought a cheapy 5 string from BCer Josh to use at dodgy venues and leave at the rehearsal studio. It very quickly became my main bass. Just so perfect in every respect. It was an OLP Stingray. I figured out eventually that it was the string spacing that made all the difference for me. So, I invested in the (nearly) real thing, a USA SUB5. Wrong move as it didnt have Stingray spacing however, it did have the sound. So, as I wasn't playing 4 strings any more, I've just traded my 4 string Jazz with Skidder's MM Stingray 5. I'm now a complete convert. Great tone, perfect playability and due to mine having a Glock preamp, has active passive option so only need to take one bass to gigs as I used to panic about batteries dying.
Not sure about any USP but have to say, in my case, it covers all points. Build quality, tone, playability, retains a decent resale value, great to look at and allows me to cover any genre of music. Studio techs and sound guys love them too. They know exactly how to mix them.