VTC5s are great. They both are 30 amp, but the vtc5 is 2500 mah whereas i believe the vtc4 is 2100 mah. I have a few vtc5s and love them, but not as much as my 35A purple Efests!!!
I'm in the opposite camp - I have VTC5s and Efest purples, and I notice a harder hit off a fresh Sony, and that the "fresh" feeling lasts longer than it does with my Efest. Wife and I both have a pair of each, purchased from a reputable vendor (Mt. Baker), so I'm trusting they're legit.
OP - in addition to an ohm meter for your builds, you need a digital multimeter. Lots of people hate on the cheap ones from Harbor Freight (they were free until a month or so ago), but I've got pretty accurate readings comparing mine to a guy I work with who shelled out $40 for his. Here's a tutorial on how to use one:
http://altsmoke.com/multimeter.html
Use one every half hour or so on your battery until you learn to judge your charge level based on the performance of your mod - it shouldn't take more than a week or so until you can guess with pretty good accuracy what voltage your battery is putting out. Once you hit 3.7 volts, time for your battery to hit the charger.
I strongly recommend you keep your builds in the 1.0-1.2 ohm range until you've familiarized yourself with using all the proper tools and can vape your battery by feel to within 0.1-0.2 volts of power. I started there with 30g wire and have gradually worked down over 2 months to where I'm now building 0.4 ohm dual coils with 26g. 0.2 ohm and below is where you can really run into battery safety issues, but that's not to say malfunction or operator error isn't a significant concern at the 0.3 you're pushing now. At least you have good batteries - I say stick with the VTC series (3, 4, or 5 - all the same, but the bigger the number the better the battery life), but that's my personal opinion only having one other battery to compare with.
I'm guessing you're using a good charger like a Nitecore, Xtar, or Efest, but if you're not you should be - run like hell from the ones that are just like a big wall wart and any battery with the word 'fire' in the name.
As far as a coil's lifespan, it can be pretty long - I usually have to re-wick with fresh cotton every 2-3 days, but if you do a good dry burn (hold your fire button until the coil gets red, release, repeat until it stops smoking) I've heard of people getting a month or more out of them. My current setup is about 3 weeks old and dry burning isn't quite knocking all the crud off, so I'll probably re-coil next time I re-wick.
Hope this helps you find a better (and safer) vape going forward!
