What are you running it in? Heavy duty and big loads or just normal daily driving operations? If you not extending drain intervals and not running abnormal (over 7500 miles) long drain cycles just use whatever is cheaper.
Personally, I run Kirkland 15W40 in my 01 Ram 2500 Cummins at 5000 miles intervals. Currently its driven highway 3 times a week 60 mile round trip and might pull 10k trailer once every 2 weeks, not very heavy duty at all. I've sent out oil test sample to Blackstone labs about 40k miles ago and they said I can run up to 7500 miles on that oil. I'm going to put another 10k miles and do another test. to see if anything changed.