I don't know why I even bother to read these things...I think the temp range and viscosity range published in the Honda manual, from Honda, knows the bike well enough to describe what oil you can use. Not to mention our bikes have a pressure relief valve behind the pump that allows excess from a higher preset pressure to dump back into the sump.
Shear stability is governed by the viscosity ranges, and narrow ranges do typically shear less over time. But going from a base II/III blend to a full base III offers different shear properties, regardless of the extended viscosity range. Is it better or worse I can't say and no one else can either, as any published claims are from the manufacturer themselves. I simply choose to run full synthetic Rotella in the summer, and it's only available in 5w-40. If they had a 10w-30 would I run it instead? Probably.
Run 5w-30 if you want. Run 10w-30 if you want. Run 5w-40 if you want. There will be no difference between them, and no significant difference in oil pressure between a 30 weight and 40 weight. If you do have a big enough difference to matter between 30 and 40 weights, then it's because your bearings are too far worn and the clearances are too wide, and you have a bigger concern than oil weight to contend with.
