the short ones, the XL's or the non-clear CE2's.
I can't get all 3
I can't get all 3
They are no differents in the inside of the clearo's and the CE 2's, and with mine I have not needed to modify them out of the box. I have had very few problems with the clearomizers, but if I do I either throw it out like I would a cartomizer or mod it with a syringe that I cut to same length as and replace the clearomizer tube that cracked. With the syringe tube it will never crack, so once you make one you use it over and over if any of the original ones fails and just pop it in the syringe tube and your back in business. The only difference is the CE 2 will never leak because it is metal and the clearo's will sometimes crack because the are plastic. I do like the clearo's because you can see the juice level .I'd say the regular, non clear. I think they'd be the best bet for use out of the box with no modification.
Short black! I know I'm in the minority on that, but those are the ones I put on dh's PV (yes, I do all his filling for him. ) The clear ones crack no matter what you do with them. Dh has an air-brusher's touch with them and I still wound up trying to get juice out of slots of his PCC. I like dripping, so personally, I vote for a regular sized rebuild-able 510 atty.