Why will I not use unmodded metal CE2 or the clearomizer:
1) Cleaning! - If you take care of your CE2 cartos, they will last quite a while. I've had some of mine which was purchased nearly 2 months ago that still work fine. To clean it you just take off the syringe tube, rinse the carto in boiling water, pat dry and dry burn, dry the wick and you're set to go again in 10-15 mins tops. Cleaning a CE2 has never been easier. "Leave it to dry for another 2-3 days" just doesn't work for me as I have limited amount of CE2 and not enough to have one for each flavor. CE2 cartos is expensive enough in the market anyway.
I have took out the metal casing of the CE2 and have never succeeded to put them back together without leaking, the same will go with the clearomizers. Plus, dry burning will take longer after a rinse if you do not pat dry the wick first.
Some liquid will gunk up CE2 within one fill, most Dekang PG liquid will last for about 5 refills before you have to clean it.
2) Liquid level - that's the advantage of the clearomizer, but if you can't take the tube off without leaking after you put it back together, no thanks. Don't wanna pull out my epoxy glue everytime I want to clean my carto.
3) Wicking - because the syringe tube is a tad bigger than the original casing of the CE2, it helps wicking by giving more space for your wick at the ceramic cup. Helps especially if you want to use lower resistance version.
4) Spare Parts - When you're finally done with one CE2, I mean they will degrade with time. 2 months is a good lifetime depending on your VG content, more VG for shorter lifetime. You get to keep the syringe tube and use it on another modded one or keep it for spare.
This is just IMHO and if I get to choose which one is the best reason to mod your CE2, it is the cleaning part!
One more thing, that soft plastic drip tip is not made well IMO, they have weird plastic taste to it...perhaps must rinse them in hot water first...