Which is better, a built-in battery or a swappable one?
There are advantages and disadvantages to either option.
If the designers make the battery swappable, the battery has to be smaller and with less capacity than if it had been built in. The designers also have to include a backup battery to keep the device from hard resetting when the battery is out. Basically, this means that using swappable batteries adds to the cost and complexity of the device, while reducing the amount of time it can run on a single charge.
Of course, with swappable batteries you have the option of buying a second battery, which significantly increases the amount of time you can use your device. Very convenient, if you are willing to put down $50 or so for a replacement battery.
Even better, some companies sell high-capacity versions of their batteries. These are physically larger than the standard ones, but often offer double the battery life. In combination with the original battery, this gives you triple the battery life.
However, the situation isn’t completely black-and-white. Even with non-replaceable batteries, you have mobile recharging options. You can pick up for about $12 an adapter that will let you recharge your handheld with a 9 volt battery. Not nearly as easy to use as a swappable battery, but much cheaper. A single 9V can go a long way towards recharging most handhelds.