In order of increasing mAh: Sony VTC 5, LG HE2, LG HE4 (can handled the heat just a bit better), Samsung 25R (aka the Mighty Smurf, even though they're green now), LG HG2.
The first four cells are all 2,500 mAh and are essentially the same battery with a few quarks. The VTC 5 is hybrid cell and will actually benefit from a few low power discharges to break it in. After that it will hold voltage a bit longer. The Samsung can take a beating right off the rack. The LG HG2 is a 3,000 mAh cell.
I'd recommend buying at liionwholesale.com. Prices are $5-$8 a cell and shipping is prompt and at a fair rate.
That said, this is something people don't seem to realize, these are all 20 amp continuous discharge cells. Do not run them over 20 amps. They can all take a 75 watt load without damage, but you should not push them past that. Respect your batteries. They'll last longer and preform better.
Here's a bit of math for everyone:
P=C*V
So, C=20 and V=4.2
P=20*4.2
P=84
At full charge each of these cells can handle an 84 watt discharge. However, nominal voltage is 3.6.
P=20*3.6
P=72
So, at nominal voltage each of these cells can handle 72 watts. It's close enough for me not to sweat it. Besides, I'd think that anyone who vaped at those wattages would get a dual battery mod to have better battery life over the course of the day.