Generally the box-type ones are better quality, and they tend to have universal connectors (510 type) so you’ve got more choice about buying a tank. I think Ego batteries (the pen type) come in at something like £10-£20 a pop. Because mine came from a wanky vape shop they used to fleece me for £25. Sometimes they’d last six months, sometimes one month and one I bought wouldn’t even charge up the first time. So a lottery.
Like @profk says, the trick is avoiding all the wanky vape-culture stuff. If you’re going for a box battery, pretty much the only thing you should care about is the energy storage which would be a number like something like 1300mAh. At a low resistance that means I have to charge it pretty much constantly, so I bought one about three times bigger, which just about lasts a day.
Also the fact that the liquids now have to come in 10ml bottles means you need tonnes of them, and the price racks up there too.
If I was making a recommendation now I’d suggest a brand name box and 510 tank. They’re probably all the same. You’ll probably find the pen doesn’t pack enough punch for you.
