6,000 miles on either of those oils is a no brainer.
Drive 6,000 miles and get an oil analysis to see how your truck is on oil. No need to do an a oil analyais every time, just to see how you engine is doing and how oil holds up it it. With your driving conditions, you should be able to go considerably over 6,000 miles once you find out how your oil's holding up.
You can get some useful free advice by posting your analysis results here.
Or you can get some better advice by spending a few dollars more and get Terry Dyson to interpret your results. With Terry you don't have to try and figure out who is giving you good advice and who isn't.