1. Did you experience an increase or decrease (or no difference) in FPS? Approximately how many frames?
FPS seems to be good (60-70fps) compared to gtaN. After awhile it seems to drop to around 30-40 FPS, restart fixes the issue.
2. Are you crashing more or less (or no difference) in GT:MP than you were crashing in GTA:N?
About the same.
3. Are you having desync issues more or less (or no difference) in GT:MP than you were having in GTA:N?
Crazy desync the first hours of GT:MP being used.. People floating over ground etc.. Seems better now.
4. Are there any more performance differences between GT:MP and GTA:N you'd like to point out?
Nope, more or less the same.