When I compared the PH610 to the PH1200, I found the 610 to be clearer voiced, deeper sounding, and a little louder... If you've A/B'd your 1200 with your 412, you've probably experienced something similar... The 610 is not quite as mid present as the 412, which itself isn't quite as mid present as the PH215... The PH215 has a voice similar to the old Deisel 215s, except with a little more sparkle up top, and a bit stronger lows - roll off the horn attenuator, and it's all "old school" 215 sound, baby...
You're right about Mesa cabs sitting in a band mix well - also, they can really take anything an amp can dish out, are stone reliable, and can get really loud...
- georgestrings