I ran 17s' and they were nice but I didnt like the lack of sidewall. I ran them because I had no beadlocks and wanted to clear the bigger 3/4 1ton brakes.
Now I'm going 16.5 beadlock because I run 44s' and the 16.5 is almost as common as the 15 :cheer:
My choice between 15s' and 17s' would be the 17s' :awesomework:
With 42's and 17's you have less chance of falling off your tire. I've seen more rigs fold a 42 over a 15 than over a 17. Ask your wife, 2 extra inches is important.