I personally find the M05 is smoother and easier to drive fast. I think the M03 is easier to get fast..but at least on carpet the M05 is king in my eyes. I ran the 03 for many years and its proven to be fast and tough. If someone asked just starting out in mini is say go with an 03 because its cheap, easy and plentiful...if they were gonna spend time tweaking and setting up and wanted to race tcs ..id say 05. I remember last time at the Memphis tcs, the 05 was 1/2 a sec a lap faster than very well set up 03s..maybe it was the long wheelbase