It really is a matter of what you want out of the bike, i.e. capability. I have a 21 speed derailluer set up on my touring bike, but on my commuter I have an eight speed internal gear hub (IGH).

Big Picture, the UGH is easier to use, but not as efficient. I have a single front chainring with chainguards on both sides of it, so no worries there. If you are running a single front chain-ring, some kind of chainguide/guard is very useful, but it sounds as if you already know that.

On my IGH (Shimano Nexus), the gear range is very well thought out and perfectly useful for my commute (mostly flat but with a few climbs). Most of my ride I spend in gears 4-6 using 3 as start from stop and 1-2 on tough climbs, gears 7-8 on the corresponding descents.

Rick / OCRR