Umm... 10,000 > 7200. Doesn't matter if you're sharing files over a 1 gigabit connection.
If you mean faster to heat your server room and run up electric bill, then the 10k rpm drive. It's also much faster to fill up. A drive that old will also be faster to fail.
The short answer is: "if you have to ask whether you need 10K SAS drives, then you probably don't need them or you're in over your head" ;)