Personally I've had some issues with ads getting through 5 on a few devices. Version 4 always works in those cases, even though it's a bit less efficient (apparently).
Separate of that it also works with VPN Tunnel, which is great for getting around cell providers that block tethering.
I bought a first gen Sansa Clip ages ago on Black Friday sale and fell in love with the damn thing. Small but not too small, good controls, good sound, intuitive UI, uses universal drivers (not a sure thing at the time), even has an FM radio built in. I've picked up so many more advanced devices over the years but I keep coming back to it. It's just a solid piece of hardware.
Also you can install Rockbox on it and play DOOM, if you're into that sort of thing.