Up to around $35-$40 I'm okay with fixed batts. I've got 6 iSticks and even the 6 month old i50 is still plugging away (though one i30 did get dementia... it's "autofire" unsafe now).
But for higher priced mods, I prefer the replaceables. It really is that "now it's a doorstop" issue.
I have a VS DNA40 with a soldered in battery. The small size is nice. When the battery goes I'll just solder in a new one. They can all be replaced if you can do the job, even the Lipo's.
The thing I don't like with a fixed battery mod is you can't vape it while it's charging.