my first "high end" knife was a benchmade pardue auto, which is tip down. i carried this for several years and got accustomed to tip down.
when i started venturing further in to the knife market, most of the knives i liked were tip up, ie, sebenza, sng, etc. after carrying a sebbie for a while, i then got used to tip up. most of the folders i have purchased in the last few years are tip up, or at least have multi positional clips.
i now prefer tip up, mainly because that is how i have been carrying for some time. i still have a few tip down only folders, but rarely carry them. and i always carry in my back pocket, right side.
i don't find either faster or easier to draw, in and of itself. it is mainly a preference for me. though i do see the logic of dip down for front pocket carry since the blade will be held in place by the pocket seam.
regarding autos, how much does it really matter whether it is tip up or tip down if it opens in your pocket? seems to me both could result in some unfortunate wounds in unfortunate places.