I have both types.
I rarely use the one hand opening feature as the action of opening a knife is to me thinking time of how to tackle the job and do it safely....
Lastly, this speed thing is to me a very modern thing. Thought up by those in a hurry... a hurry to cut themselves. Take your time, think how to tackle the task, and then you will find its done faster than if you just hurry and get it all wrong. Works for me. (Its amazing how fast you can be in extreme situations, keep your head and you have all the time in the world).
This.