A 50 weight will always protect better than a 30 weight by shear virtue of a thicker hydrodynamic barrier. Now, whether it's necessary and/or we are willing to pay a fuel economy penalty for it is another story. HT/HS numbers are probably important because they give an indication of how well an oil stands up under punishment..but, it's only 1 test.
I believe the UOA's don't give the whole story. Traditionally, thicker oils have been used and are recommended when 1. racing (high temp/high punishment conditions) 2. long drain intervals (I can't see too many engines going 10k mi. intervals on convenience-store 5-30) 3. engine life is a priority (Euro. engines last longer than U.S.).
Suffice it to say, you may be fine by using a convenience-store bought 5-30 if changing every 3k or less...I've needed to do that for years. Otherwise, these U.S.-created thin oils will slowly allow for burn-off and build-up necessary for most of us to use auto-rx and the like because we are just talking about the side effects of using these oils rather than dealing with the real issue.