If cost is your only concern, then there's probably nothing else to think about. But even a rental is something you own, and investing in it, like anything else hopefully, increases it's value. You say you're only goping to hold onto it for a ferw years, then let it go. My experience is that most people who own rentals do so for one reason; to make money. not to spend it, so new windows may not even be an incentive to the next owner.
Personally, I don't like alside windows, at least not the ultramaxx. Cheap vinyl, 7/8" glass pack, aluminum intercept spacer, only one side of one pane of glass treated with the lowE. that window shouldn't cost you too much to put in, and in 5 years, when the next guy owns the place, he can deal with replacing the windows again.