I think "Background services" because of SQL and SP services, but maybe there is other best practice?
1 Answer
Background services is the way to go for servers, SharePoint has a lot of processes running in the background and none or almost none running as programs itself. What this setting does is to give the program or background service the priority to recources of the machine.
clients like windows 7 and 8 run with the setting on "Program" since they need to open and run a lot of client side applications, some forums advice at times when a program freezes a lot to try swapping to "Background service" but (user) clients are best in "Program"
you might want to look at task manager, this will give you an idea of what runs as program(application) and what as background service.