I actually own a M2600 16input but I've seen a deal on a M3500 32inputs.

How is the M3500 compared to the M2600? are the pre worst, better or the same? I record with an analog 24trk so actually it is always a pain in the ass to mix with a 16channels board but if the overall quality of the m3500 is not as good as the m2600 obviously I won't change...