hey welcome. I have had 2 NSX's and 5 M3's (3 E46) They are both awesome cars, but very different. Personally i liked my M3 better for daily driving, taking fiance to dinners, friends out on town, etc. It was more a really nice sports car with easy everyday living. More luxury sport IMO.
the nsx has always been one of my fav's. I love the look, its rare, and its much more purpose sport imo. I drive it only on really nice days, usually alone just to enjoy the car/sounds/feel.
My M3's were all VERY custom/built...AC, HRE, KW, AA SC, etc, etc...tons of $$$ lost in them (almost like the stock market now..lol)
I wish i could have both. Came down to me getting another NSX cause i never drive much (travel too much) and so the NSX was a perfect sunny day smile machine for me.
My last M3 was N/A and yet had a ton of mods..it was maybe 360hp (flywheel) while my NSX has I/E/ecu (similar mods) and is maybe 310hp (flywheel) however the nsx is much lighter. I think the M3 is "quicker" but the NSX is "faster" in that i mean, the M3 is a super light to light, squirt out of corners quick..the nsx just builds speed and is super stable at higher speeds. I LOVE the steering feedback on the M3 (e36 was better yet!) and the brakes are nice on the M3 (mine all had huge brembo's thou) The NSx has a MUCH better transmission/shifting. The NSX is dead reliable. My M3's were too..occasional ignition coil and such..and yeah my 01 had the bearing recall..but even boosted my m3's never missed a beat. In fact my 01' with the AA SC kit made over 400RWhp and the guy now has over 80K on it.
I was on the list for the 2nd M3 here in portland but once i saw the new M3 (E92) and drove it, i was like 'yuck" too heavy, no tq, no individuality, too much $$. My buddy has a new M3 and drove my NSX "dude, this thing is way faster than 290hp" i laughed...i said "well its 800lbs lighter, shorter gearing(i have type R gearset) and actually makes TQ! (obviously his new M3 would SMOKE my nsx, but the m3 doesnt "feel" fast..it just is!)
Good luck and ASK a lot of questions on here, it helps!!
Feel free to pm me if ya want, i'll shoot ya over some pics of my M3's/NSX so you can see and you can ask me specific questions if ya want.