The benefit of a lanyard partly depends on the size of the handle. I have one fixed-blade with a small handle, and that is definitely easier to use with a round-the-thumb lanyard. I also have an RSK MK3 which has a handle big enough not to need it. I've just given it a small loop which I can clip to a carabiner if I need to.

If you drop it, I suspect the lanyard is a net gain in safety as it will prevent it falling far enough to build up the speed needed to do more damage. Plus you are less likely to drop it in first place, plus it may make you less tempted to try to catch it.