Well, while you have some good points, there's a few things I'd like to mention. First, an M3 NEEDS to be a versatile multi-role platform IMHO. Interception is for M4/5s, so speed is nice but not primary.
Second, the M3 is a GREAT capturing platform. Sure the Iguana is nice too, but unfortunately its MUCH larger and handles like a dog compared to a Nova. You're more likely to ram or be rammed in an Iguana than a Nova, in my experience.
The turret on the back with an AIRE is a great missile deterrent, allowing even 'n00bs' to live through difficult encounters heh.
Fourth, the Perseus may be a good fighter, but its cargo bay is just too small to be useful as a primary Player ship, unless you plan on docking to a cap ship after every engagement, in which case, firepower's not an issue!
Fifth, I have utter contempt for PSGs. I mounted them once on one of my ships, saw what they did and how they worked, and then immediately sold them. Just the idea of a 'laser shockwave' is preposterous, but oh well. Also, the Perseus can ONLY mount AHEPTs, not the Beta version, so you lose quite a bit of power there.
For these multitude of reasons, I still say Nova rules for multi-role usefulness, with the Mamba coming in 2nd as the ultimate dogfighter. That's just my opinion though.