The player count is easier to raise in SA-MP. Because they have very little sync, SA-MP uses a lot less bandwidth than MTA does, and its server and clients process less data. (This is why you can't damage cars, etc.)
In MTA, however, there's a lot more data going in all directions all over the place. So even a small change in player count can cause a major change in the bandwidth and processing time needed.
It's not like you need 200 or 500 players in a server though.