Not an opinion, if you know anything about physics it will make sense to you.
Push anything hard enough it will break. Pushing a 17 inch wheel wrapped in 37's is much less likely to break than pushing a 20 inch wheel wrapped in 37s
Also with 17's you have more side wall to absorb stuff.
so thats up to you to decide on, how hard will you be pushing your truck,the quality of wheel you are buying, etc. but yes I'm sure 20's could work, however they are typically more pricey to replace if one does break and are generally more prone to breaking. I've seen a 20 inch rim folded up like a coke can on an f350 after the driver went a lil too quick.
if you want the 20's buy em dont need our opinion right?