Agree with David. I recently got a Byrd with the Emerson opener and love it for the speed and ease.
I find mora fixed blades with plastic sheaths pretty easy to get the knife back in.
To be fair, with knives I think the importance of speed is only relevant while deploying. It's a tool. It's (sometimes) important to have it ready for use quickly. When you don't need to use it anymore, you can spend some time putting it away safely.
I find that a knife that I can easy deploy and put away without thinking much to be very helpful, especially if you have your hands full. E.g. as a non-car-person I transport everything with my bike and it happens quite frequently that I tie some heavier load on it. So, when taking it off I need to steady the bike, hold the cargo and cut some strings. That is where a knife that deploys easy and vanishes back into the pockets without any hassle is appreciated.
While my Mini Grip is a fast knife is not even in the same league as my Delica with Emerson wave when it come to deployment. As for closing my Grip is easiest and fast. I carry a fixed blade when working and thats what I reach for first. Its quick to deploy but depending on which I carry it does take time to re-sheath.
CRKT Seismic