There are advantages and disadvantages, of course. A fixed battery pack is generally better for a person who wants to vape and not mess with it; provided you don't mind your mod being a disposable. With removable batteries, the primary advantage is speed of recharge. Just pop in fresh batts and you're good to go. They take as long to recharge, mind, but they don't leash your mod to a wall wart or car lighter plug while it's happening. That same, expensive, stand-alone charger is also an advantage, provided you pay for an expensive ($30-50) one. With fixed batts, you get a charger board the size of a dime and a LED that turns off or on or changes color when it's charged. A stand alone charger has better electronics, more safety features, and good ones with an LCD readout tell you a lot about your batteries; enough so you can figure out when it's time to take them out of the hi-powered contest mod and swap them over to your low-power pocket puffer, or replace them entirely. You don't get surprised like that, as happens when you plug in your iStick the day before leaving on vacation to discover it won't charge any more. Another advantage is expense: removeable batteries cost more to start up because you have to buy twice as many as you need for spares, plus a charger, but the life cycle cost will be lower because the electronics in a good mod last longer than the battery. Thus you can just buy new batteries instead of replacing a perfectly good mod with a bad battery in it. Extended life away from power can also be done with removables; just take extra spares on the week-long camping trip. Removable batts also open the weird and wonderful world of mech mods, for those who may one day be so inclined. (I'm a mech modder, for example.) Finally, good quality IMR batts use safer chemistry than LiPo packs. LiPos can be and are used safely every day. They also offer better energy density (more electrons in smaller space) but they merit the care and attention something that small and powerful deserves, and usually doesn't get from the kind of owner who wants to plug and vape. The RC helicopter types have smaller, lighter and more powerful batts than vapers. It's significant the chargers for those batteries are more expensive than a good Xtar. Those RC troops take care of their batteries, too, as they are expensive to replace. You don't have to buy too many batteries before figuring out taking good care if them is a good idea. This is easier to do with replaceables.
