As to the "5 piece", yes you are technically correct, I was only referring to the urethane pieces. Powerflex's front bushings also are 5 piece.
As to stiffness, my experience has been that when it comes to urethane, the color typically is an indication of hardness, both are yellow, but of course I'm sure density varies between manufacturers.
As to the M3 bushings...my only two reservations about those...
-They are rubber and steel...rubber in my experience degrades quicker in dryer hot climates...say...Arizona!
-while not a huge consideration, the 1 piece fronts are not as appealing as the 2 piece from an installation perspective as long as there is no compromise in performance.
Who makes those red ones? Are they 2 piece...kind of looks like it? No steel bushings and no steel washers?
2008 E88--2 years on 100% E85. Too much to list..
2008 E60--JB4/MHD--FBO and under development
2011 E90--Fuel-It! Stage 2 LPFP + TBI--Pure Stage 2 Turbo--JB4/Flash--VRSF 7" FMIC--DP 538/581
2013 Mini JCW--Tune--DP--FMIC--a couple Fuel-It! goodies