With RAID10, you’d have 8TB of storage that is both striped and mirrored. You’d get a 4x increase in read speed and a 2x increase in write speed. You’d be fault tolerant against AT LEAST one drive failure, possibly two depending on which drives fail.
With RAID5, you’d have 12GB that is striped and parity checked. You’d get a 3x read speed increase and normal write speed. You’d be fault tolerant against a single drive failure.
With RAID6, you’d have 8TB that is striped and parity checked. You’ll have a 2x increase in read speed and normal write speed. You’ll be fault tolerant against two concurrent drive failures.
I recommend RAID10 if you want the all around speed boost and fault tolerance but don’t care so much about capacity;
RAID6 if you care more about redundancy;
RAID5 if you want a read speed boost and more capacity with a little fault tolerance mixed in.
There’s also raid 0, which is gonna be hella fast all around but god help you if somebody farts too aggressively next to it; and raid 1 if you just want 4 redundant backups of the same drive.
Personally, I’d go 10 unless you just really want the extra storage.