Is there any other difference?
There are a lot of differences.
- Servers often come in 19" format for easy rack mounting. (not so important when you only have one of them. But very important once you have a few dozen or more).
- Server hardware is build to last. E.g. typical fans on servers are designed to run at least 5 years for 24 hours per day, 365 days per year.
- Servers often come with redundant hardware? E.g PSU failed? No problem, we just use the other PSU and you can replace the broken one without the server going down. Again not so important on a small scale. But a PSU failure on a fileserver which causes problems for a few thousand people (and thus wasted a a lot of man-hours) is expensive.
- Servers often come with chip sets (or CPU's) that support ECC RAM.
- Server class hardware often supports 'bigger' computers.
- Server hardware is often better tested.
The RAID is not important. I can put a nice RAID card in a desktop. But a good quality RAID card, tested with the motherboard and the drives is has less unpleasant surprises. If I buy a server from HP I usually add a HP (400) RAID card, and HP branded disks. (with HP firmware and well tested by HP). Same for Dell (Replace HP 400 RAID with PERC RAID).
New (not second hand) servers often also come with 3 or 5 years Next day guarantee or better. And the manufacturer will have spare parts for it. Guaranteed compatible spare parts. (Just because a desktop component has the same name does not mean it has the same hardware or needs the same drivers as the identical named part sold a month earlier).
I could probably go on for a bit, but briefly: Yes, there is a difference. and if there was no difference people would not pay the premium price for server hardware.
See also the post What are the Benefits of Server Hardware? [closed].