have carried tip down (ie BM 800/910/MT SOCOM elite/Maxx design/crawford kasper and perfigo) and tip up (ie EKI CQC8/CQC7/I&I tanto/SOCFK etc ) and really have no real preference.
the only 2 knives i have had open in my pocket were tip down (ie spyderco gunting and kahlsa) so go figure. on both my finger caught on the horn and started it opening in my pocket unintentionally, sold the kahlsa and got a skunkworks for tyhe gunting, so fixed that prob. incredibly, the kahlsa was my first venture into "high dollar" knives (ie over $50 or so) so i was VERY dissapointed, thought they all were like that, but have since learned diff.
right now into EKI's, so only one way to go, even though my favs arent waved (I&I tanto, CQC8 and P-Tac) but i do like to put a fob made of light paracord type material (like MT does on the SOCOM, etc) to help w/the draw, and do kinda like that, so i guess i kinda prefer the tip up for that reason. a tip up maxx 5.5 would be a bad boy, they do wave pretty good, but i would be carefull carrying one that way, just cuz' DDR says not to, and they do look like they MIGHT be prone to it.
have NEVER had a prob w/EKI's opening in my pocket, not even a little tiny bit, do keep the pivots reasnobly tight though, nor on my buck strider 880 or spyderco matriarch, either. that 880 would be a mess if it opened up, though lol.
agree, a cheap knife can open up but i think tip up/down might not make a diff if the knife is a POS anyway.
must say to me it really dont matter, design makes more diff to me.
greg