This is what scares me about flat water flips. Off surf, you not getting "yanked" around...... It is smooth.
I can not really compare as I have yet to ride surf, but I would guess this to be true. As a rule you are looking at more horse power and more body motion to get the flips around on flatwater, so it's easier for your feet to come out of holds or hands to come off grips. Both of which end in pain usually.
I've landed on ski face first and had ski land on my head, either time had I not been wearing a helmet i'd be hurting to say the least. Got hit hard enough to black out WITH the helmet on if that tells you anything lol. That was off a big cabin cruiser boat wake though.
No experience on vwakes but i rarely see a clean one so I would think a normal wakeboard wake would be a little easier to time and setup for vs just hucking and praying off a vwake whitewash.
tl;dr i know nothing but flatwater