Favorite feeder / burner is the Penelope. I've tried lots of sweat-shop atties and cartos, the FOG, the UFS, and several Genesis atties, but none compare to the vapor quality I achieve with the Penny. I also highly recommend getting the Kir Fanis clear window for it, as it really lets you see what's going on and how better to use your Penny -- when to close the juice control to bleed out air bubbles, when to refill, etc. I have three Penelopes -- one never used, and the other two in rotation so that I can use one while I soak / dry / re-wick the one on-deck.
Favorite power plant is a little more difficult. For the experience / vape quality, I've got to go with the P+ 18500 with the Kick and an 18350 battery. Using the Kick, I don't have to experiment and dial in the proper voltage for my coil of the moment, nor does it affect the vape when my coil randomly decides to change its resistance as coils are occasionally wont to do. The P+ has the friendliest fit to my hand -- the perfect size, weight, balance, everything.
The only drawback is that the Kicked 18350's tend only to last about 2.5 - 3 hours. So I really only vape on it when I'm at home and can replace the battery with ease. For some reason variable wattage doesn't seem to be as efficient as variable voltage to me. It's a trade-off. Variable wattage gives a better, more consistent, more pleasant experience, but also less time between charges.
I've got an extra charger and four more IMR 18350's ordered, so the only-vaping-this-at-home thing might change in a few weeks.
Compare my 700mAh AW IMR 18350's on the Kicked P+ (my most expensive combo, by the way) with a 650mAh eGo Twist, my second favorite and least expensive power source. Even cranked up to 4.8v, the Twist gives me about 9 - 10 hours vaping time.
The 650 Twist with the Penelope is a little top-heavy, though. But its performance is very impressive, considering its diminutive size and inexpensive cost. Even ignoring cost and size, the power it produces is very satisfying.
I've also got a ProVari that I use with 18650 extension sometimes and without sometimes, depending on my mood.
It performs very well, has great battery life (all day and more on a Panasonic 2250mAh IMR 18650), but it's thick and and heavy. It's loaded with useful features, but in daily use it's my third favorite. Aside from using it to test my atties, I don't vape with it as often as I do my P+ or my Twist, mostly because its bulky mass makes it feel like I'm vaping on a Maglite.
The 900mAh Twist is long and silly, like vaping on a baton.
I get over 12 hours of vape time out of it, and its power output is just as satisfying as my other mods. I'm not a big fan of the length, though. It's about a cm longer than my ProVari with 18650 extension, making it my longest mod.
But, after vaping variable voltage and variable wattage, all these devices offer a more satisfying vape than anything that's not boosted.
Whatever mod you choose, pay attention to conditioning your batteries as you break them in. When you first get your battery, charge it to full. Then vape it till it's completely spent. Then charge it to full again, and repeat the cycle at least 4 or 5 times. After that, you can do pretty much whatever you want with it -- pull it out and use it halfway charged, charge it when it's still got power, whatever. If you shelve any batteries, don't store them fully charged. Instead, store them with about 3.6 - 3.7v of charge (about 3/4 the way spent if you don't have or don't feel like using a multimeter). If you do all that, unless you short your batteries or otherwise damage them, they'll last for years, maybe forever.
My Ego Twist isnt bad either with an ego 2.4 ml cc or dripping with a 510 atty 
