Yeah, great thread.
My two cents (4 cents?):
1) My guess is cut quality is similar when the cutting units are maintained by a good mechanic. Green speeds may be fast or slow, but it really has nothing to do with walk vs. ride. Just as an example, the absolute fastest greens in my area are triplexed.
2) The issues collar/surround wear are always going to be an issue, largely because of the tires. A turning tire is just hard on turf. A skilled operator can mitigate some of this by being gentle, but that adds time to the process and it's hard to coach. Best example of this was at Old Mac where you could see tire tracks where every triplex turned on the surrounds. My guess is they would never be able to walk mow with their greens acreage (They'd need like 7-8 walk mowers maybe) so it's a necessary evil. As for cleanup passes, you can have a couple guys walk mow the cleanup passes, but then you're looking at a similar labor usage to just walk mowing all the greens (e.g. 2 guys triplexing, 2 guys cleanup, same as 4 walkmowers).
3) The diesel electric stuff looks great, but our mechanic says that it's far less durable and needs to be adjusted more than the older hydraulic units. For example, if the operator falls asleep and jumps a curb or something the thing is toast and needs to be readjusted. It is nice to not worry about hydraulic fluid leaks though.
4) USGA and other sand based greens seem to be fine with triplexing impact but I wonder how they do on older pushup topsoil greens? Do you see all three tires in the form of depressions after a pass?