BMW M3 E46 CSL - According to Auto Motor und Sport in the Top 10 of the most wanted BMW M3/M4 Models of all time. Only 1383 were produced between mid 2003 and 2004...
According to Jim Clarkson (Top Gear): "...the most hardcore BMW ever made."
So +1 for the M135i or +1 for the M3 E46 CSL
Head to Head:
BMW M135i (Automatic): 2979 cc R6 turbo (N55B30)
Weight: 1515 kg / 3340 lb
Max output: 235 kW / 316 bhp
Weight to Power ratio: 10.76 lb/bhp
Max torque: 450 Nm
Sprint 0-62mph: 4.9 s
Top speed: 155 mph (limited)
BMW M3 E46 CSL: 3246 ccm R6 (S54B32HP)
Weight: 1385 kg / 3053 lb
Max output: 265 kW / 355 bhp
Weight to Power ratio: 8.6 lb/bhp
Max torque: 370 Nm
Sprint 0-62mph: 4.8 s
Top speed: 155 mph (limited)