I own both replaceable and internal chargeable, I love my istick TC40w. Its small and works well for when I am at work. I also just invested in a Kangertech Subox setup, and I am loving that one too. With the internals you will have to just wait for it to charge before using it again unless you can vape while its charging. Not all internals will allow you to do that though. The advantage and disadvantage to using a mod with replaceable batteries is that you have to have them on hand. When the battery is drained just pop in another one. Some people don't want to have to carry around a bunch of rechargeable batteries everywhere they go though and there's no need if you know how long a mod with an internal battery will last you with your vaping patterns. The rechargeable batteries can last vastly different times depending on the mod and the type of battery.