Whoever said about the mechanicals having efficiency problems is right, and I am an engineer. It's the CONTACTS, baby. If you want to check it out, take some 90+% alcohol, isopropyl or ethanol or whatever, and some q-tips, and thoroughly scrub the battery ends, the contact plate in the XL, the spring etc. If you have real contact cleaner, so much the better, but alcohol can help a lot. You'll be surprised. We lose like almost 1/2 a volt across all the funky connections in the XL circuit. An electronic device switches the big current with a transistor, that has minor losses compared to dirty mechanical switching. It's just a hassle cleaning the contacts, so I don't bother, i just work the switch hard to get the gunk off.
As a chain vaper I swap 18650s (AW 2600 mAh blackies) in the XL several times a day. Like Ukeman said, there's no free lunch. You want heavy hitting, go with Low Resistance. You want heavy hitting and veeery long battery life, dream on. It's just not possible.
Now I've taken to using the NiMh 5 volt stacks in my second XL with a 2.8 ohm atty. The short life on the NiMh doesn't bother me around the house, I'm constantly swapping and charging anyway. When my wife's around, sometimes there's a queue at the chargers, a battery or two lined up next to the two 3.7 volt nests, the 5 volt NiMh bays, and the eGo chargers. Nothing's perfect.
But absolutely most of all, I hate the Provari. Not only is the user interface idiotic, every time I try to reach the AO page I overshoot and have to go around the menu. Every time I tap the button to vape, I end up on the AO page and can't figure out why it's not firing. And then the battery life is lousy. I got a couple of the eGo twists, and for the tiny battery that's in there, it's astounding that it lasts about as long as the Provari with an 18650! That Provari buck-boost circuit is just inefficient, to top off a dumb interface. The Provari was so expensive, and the finish on it is so nice, that I can't toss it. But the eGo Twist shows what VV is all about. Not getting enough hit? Turn it up a bit. Too hot, turn it down. No menus, no bs. And Joye has always made the best batteries, they somehow squeeze more vaping time out of a battery than anybody. I've taken the original eGos apart and marveled at the little battery in the tube. It's just an efficient circuit they've designed there. Now with the eGo Twists I'm rediscovering all the spare CE2's I bought.
So, Synnuh, just don't fret. All this stuff is useful, and none of it is perfect, 'cause we be humans. There CAN be more than one. We need lotsa GEAR!
About a month ago I was in Warsaw, and you know they SMOKE there. I thought the world had come to my end when I saw my friend the editor of the big Warsaw daily, a news junkie and writer who's been a chain smoker for decades, the kind with the yellow fingers and he's talking with the cigarette in his mouth and lighting the next cigarette off the last one, and he shows up for a meeting and he's VAPING!!!!! Whoa! I gave him my last two full 30 ml bottles of homebrew VG juice, I was so moved!
I recognized your nick, but didn't place it. No biggie, I love the LT, don't regret making the trade, just missing having a VMod in my hands now. 
