Unless you have a lot of tiny files being written/erased/written to the drive, basic defragmentation should be more than enough on Windows. You're going to have other factors that can't possibly be generalized...most servers you would have to factor in your RAID controller, caching, load, type of RAID, etc. to get performance. Your best bet would be to run a benchmark before and after running your defrag to get numbers for your particular circumstance on your particular hardware.
If defragging makes a big difference in your performance, I'd venture a bet that you should be looking at changing hardware a bit.
The bigger benchmark is whether your server is having performance issues and your users notice. Is that the case? Then start narrowing down the cause as to whether it's the disk subsystem and whether it's a problem with your drives being too slow, utilization is wrong for your RAID configuration, etc. rather than randomly poking whether a particular type of defrag will speed up access.