You actually gain a very good amount of performance by using RAID10 versus RAID5. Not necessarily for unrealistic single-task sequential reads, but for the absolute most common every day random I/O it's the difference between the random iops speed of a single disk with RAID5 versus the random iops speed of 3 disks with RAID10.
Try it, play with it both ways and see for yourself. Use bonnie to give you an idea of your performance difference with one configuration vs. the other.
If you care far more about amount of space, RAID5 is fine. If you do actually want extra disk performance out of your setup you'll want RAID10.
A bit off-topic for a Linux-related forum, but using ZFS I actually compromised and ended up with awesome performance (500MB/s, ~2000 iops) by creating five 3-disk RAID5's and striping them together. That's five sets of 3 disks each, losing 1/3 of my space but much better performance for it. You probably can't do that sort of setup with a normal hardware RAID controller, though. If that configuration was possible with the 3ware controller, you could compromise in exactly the same way, double your iops by doing two 3-disk RAID5's striped together.