Personally, I have found that a simple clickie is easier for a non-flashaholic to operate than a twistie. Whenever I hand someone a twistie, they never know which way to twist: "do I tighten for on" (most designs), or "do I loosen for on" (like the ever-popular MagLite). This is compounded even more if I hand them a momentary twistie (my poor mother... but it's funny to watch. :shakehead).
I don't think you would run into any trouble with a non-protruding clickie coming on in a purse/pocket. Having a clickie that is also locked out seems like more trouble that it's worth if you're actually carrying it and not simple transporting it.