Quote from E.Reiljans : Easy.
[*]Ability (for servers) to create completely custom maps (SA:MP is limited to GTA:SA's built in ones, and few ones added by SA:MP team)
[*] There are proper (complete, not just a 'example gamemode' like in SA:MP) official gamemodes out of the box
[*] Acts more like original GTA:SA in few aspects, e.g. weather changes, vehicle modding and such
:[.
Just looking at these..and I'm confused, maybe i'm misunderstanding buuut,
If you mean maps by "Objects created in a certain area on the original SA Map", then you can have that on SA:MP.
There are plenty of gamemodes being created for SA:MP, maybe not from the box, but that doesnt make them any less quality
Also, since when doesnt SA:MP have weather changing and vehicle modding?
ON TOPIC: I'm still interested in seeing whether GTA V will be just Los Santos or all of San Andreas.