I am one of the regular critics of the factory side luggage. The top box is excellent! You can buy the identical top box elsewhere, just without the matching color panel. So, if you want the matching color pay the premium from your dealer, otherwise get the black panel top box from an aftermarket source and save some $$.
I commute to work on my '15 LT with factory luggage, as well as some touring and even some mild back country camping. The volume of the luggage is ok, but I find the shape terrible particularly for work. The slanted shape severely reduces the size of a rectangular object you can fit. A standard briefcase probably won't fit. I have several soft bags, one with a tablet in it, and have great difficulty getting them to fit. The shape is also poor for grocery shopping.
For camping, having a flat top and lash points on rectangular metal boxes would be a really nice feature. Top loading would be nice. One maker has boxes which can either open from the top or the side.
In some ways the factory luggage is really nice. It mounts/dismounts from the bike very quickly, without needing any rack system. Factory bags are keyed to your ignition key. Opening and closing the luggage is really simple.
I don't totally trust the clasp though. I once had one pop open, most likely my error in closing it, but proof it is possible to think it is locked closed when it really isn't. I use little velcro wraps on the factory side luggage handles to ensure they remain closed.
Aesthetically, whatever you prefer is up to you. I don't mind the look of the factory luggage, but were money no factor I would replace them with metal luggage.
In 2015 the LT had ABS whereas the base model did not. The ABS is well worth the extra cost, though I don't know if it is standard on all 2017 versions. The ABS was the selling point for me to choose the LT.