This thread is as messed up as a soup sandwich!
Ok, Here's the deal, it's not the OE rims limiting the towing capacity, and there's a ton of threads on tow ratings.
No, the rims aren't weaker, and no they won't bend on every pothole you hit. About the only downside is tires generally cost more, now that 17s are bargain basement prices like 16s.
Whether you prefer the look.....subjective. To pass up buying a truck that is otherwise what you want based on rims? Silly.
Btw if you want 17s, there's always a grip of OE takeoff tires/rims and plenty of 17s for sale on Craigslist that were switched out for fancier wheels.