I'd suggest getting the removable cable because if that cable breaks you can replace it. If a hard-wired cable gets loose or staticky, there goes the battery box. Of course, you do need a reliable cable and you have to make sure it's plugged in.
Don't spend the extra $$ on bass roll-off. Bass roll-off used to be helpful--maybe, possibly, though I never saw the point--on recorders like minidisc units that would distort with big bass. But recorders now can handle the whole spectrum better (assuming you have levels set sanely) and bass roll-off on the battery box is crude at best. Better to get the best fidelity your mics can provide and tweak later (if necessary, probably not) than to get a recording you can't restore. It's like a photo--you apply the Instagram effect after you shoot the photo, not while shooting it.
As has been repeated here, you can do any bass roll-off with software--even software as basic as Audacity, which is free, has lots of equalization options. You can also do it with the EQ in whatever you are using to play back the music.