Leather cuffs -- they're quick and easy to attach and you can change positions and attachment points without a lot of effort (I prefer to expend my effort on the body and not the restraints).

If your submissive tends to lose control in any way and really pull, then look for ones with metal grommets reinforcing the buckle holes.

I learned that the hard way as kitten tends to lose control and likes to sink her claws into things at certain points. I was busy with something had a "what's that snapping noise? OW!"-moment.

Suspension cuffs are good too -- very sturdy and designed to be safe and comfortable when tension is applied -- but they're a bit more costly, typically.