Basically, the Prometheus kicks the Sovereign's ass, but the Prometheus AI has no idea how to fire forward torps. XD That's what I observed in these two battles.
Prometheus would be my choice of ship between the two. While not as large, it's close to being as heavily armed and armored. It's also got newer tech and is faster.
Pro could use a 25th century refit and she would be about perfect for an intercepter. Improve the geometry a little, adjust the firing arcs and make two brutally capable halves instead of gimmicky three, and perfect the regenerative shield generators.
She's the Sovereign eschewing any pretense of unassuming multi-role explorer and going warship without the Defiant look. I'd change some things for a 25th century refit, though.