For real convenience and interchangeability, I'm afraid I can't personally recommend the 510...and I started out with one! I've fallen for the
KR808d-1 in terms of ease of use. The 510 I use when I don't mind tinkering, but I find myself using it less and less these days.
The KR8 is a two piece model: cartomizer + battery. (Other models like the 510, 901, 801, etc. use a three piece design: battery + atomizer + cartridge.) The cartomizer is a neat little self-contained unit with a lot of polyfill in it to hold more juice than your usual unmodded 510 cartridge. It's easy to switch around among cartomizers to change flavors and to switch to a fresh one. They travel easily, don't need to be cleaned (when they run out, you refill them; when they die, you toss 'em), and give excellent flavor.
Edited to add: and the KR8 battery life is better than the 510s. 510 regular = 180mah. 510 mega = 280mah. KR8 regular = 280mah. KR8 mega = 380mah.
Driving is so much easier with the KR8 as well -- no dripping or refilling cartridges, I just pop another cartomizer on.
With the regular 3.7v KR8 batteries the throat hit can be a bit wimpy (IMO, others disagree)...so I got an Xhaler to use with it. The Xhaler can be used at 3.7/5/6/7.4v settings and I have found the 5v setting works perfectly with the KR808d-1 cartomizers. That combo has become my trouble-free setup.
Refilling is a little bit more work with KR8 cartos than with the 510 cartridges, but it takes me like 10-15 minutes a day to refill a ton of cartos for the next day. About the time I'd spend going out for another pack of smokes!
So my
completely biased recommendations for a plan?
1. Get a starter kit from
Vapor4Life (their Vapor King is a KR808d-1),
GoodProphets,
Nhaler, many places really.
2. Get some flavored prefilled cartomizers (Vapor4Life offers the biggest selection by far for flavors; prefilled are also available from any place selling the KR8). Buy juice to refill them with. Learn to refill your cartomizers using the tips on this site or the many YouTube videos available.
3. Find a high-voltage mod that fits your tastes and budget. Suggestions include the
Xhaler(3.7 or 5 or 6v), the
Chuck(3.7 or 6v), the
Prodigy(5v), the
GLV(5v), or the
Silver Bullet (6v) or BB (3.7 or 6v). (Take shorter drags to avoid burning the fill, and be prepared to refill more often, but these make cartomizers
rock. Try part-VG juice like Nhaler's
High Voltage juices,
Ms. T's Bakery, or
TastyVapor for a great high voltage vape.)
4. Stock up on blanks from the cheapest source (
Mist-Stix w/ code "ECF",
HealthCabin's bulk special, other vendors' specials) and fill them yourself.
Just my opinion, void where prohibited, etc. Good luck!