I'm glad I asked! The majority have spoken "M6," so I will go to a nearby SF store in the next couple days and check one out and see how it fits in my hand.
OK, just got back from the gun shop that stocks a full complement of SFs (except for the Beast). I found the barrel of the M6 to be too big
and I don't have small hands (nor large ones). Perhaps I'm just used to the small size of the A2, so the M6 is too big of a leap for me.
I really didn't care for the M4. Nice beam, but I didn't like the balance or grip in my hand.
I still liked the M3. One thing that I hadn't thought of before was how I'd properly orient the light before turning it on so that the oval beam was either vertical or horizontal. With my A2, it's easy. I rotated the lamp until the beam lined up with the clip. So, I always know that if the clip is down, the beam will be vertical. With the M3, I couldn't see any way to know since the body is round. So, I could grab the light, turn it on, and the beam would be oriented in a strange direction. Not the end of the world, but something I wanted to consider.
I went back to the C3. With anything other than a cigar grip, it actually works well. The P90 wasn't oval, so I really didn't need to worry about orienting the bulb, and if I did, I could always use the square sides and clip for orientation.
9P was also nice, but I prefer HA and would spend the extra $ to get it.
So, I'm now leaning towards the C3 with P91. I know that the run time stinks compared to the M6 w/MN15, but I just found the M6 barrel too big. If it'd been the same size as a Mag 2D, it'd be a different story. The Mag 2D barrel is really as large as I comfortably want to grip.
Any feedback? Am I off base here? Any other recommendations?