If your clients are all macs it is just nicer keeping the server on macos imo. mac os is unix after all so you don't have any software incompatibilities for tools you'd probably run on the server. Time machine support on the server is built in, instead of being a sort of hack with samba if you wanted to try and run it on a linux server. I haven't messed with it much but there might be some clever stuff you could do with applescript and triggered actions, maybe schedule your compute jobs from your calendar app for example.