Pretty much as Ken said (since he is the owner of this site , if he recommends something , i would tend to follow his suggestions) , and i am just like you and many others here , just a enthusiast with a somewhat extensive mechanical background who happens to have a lot of free time on my hands , so i hang out here because i like the people and atmosphere , and the quality of the experience i have had for the 11 years i have participated in these forums , ............. but anyway , oil is like beauty , its in the eye of the beholder , what oils one person uses or likes may not be suitable for riding conditions of another rider , or some people are just brand specific and choose based on what everyone else uses or what is locally and readily available ....
That said , what Honda recommends is usually based on meticulous testing and research , but as Ken mentioned , some of us stray from that , but usually only slightly , I personally use Rotella T Full Synthetic 5-W40 , and/or Amsoil (full synthetic) 10/40 Off-Road in both engine side and tranny side , I am also looking into Maxima (full synthetic) , but have not tried it yet , as i do like to research things before submitting my engine to a product i know nothing about , personally , the main concerns you need to worry about is compatibility with your wet clutch by meeting the JASO MA guidelines for use with a "Wet Clutch" , not viscosity so much , since most people with these bikes change their oil frequently enough , the oil will never have enough run time to actually break down to the point is is allowing excessive wear to occur , so the thicker oil is really unnecessary for its intended purpose , .... what most of us do , is run a full quart in the tranny side , as the space is tight around the gears , so if you do desert or any sustained 4th-5th gear riding , it has a tendency to evacuate the oil galley surrounding the gears , sometimes causing a catastrophic failure of the transmission , ...that said , its rare to happen now days , as mentioned , most of us run a full qt . in the tranny side , which keeps the gears and bearings well lubricated , its cheap insurance and you stay within the Honda recommendations ..... we always run the recommended amount in the engine side
The only thing i could think of gaining with a thicker viscosity oil is maybe a cooling effect which as mentioned , people that do use it are either street riding or doing Supermoto or the like , ....What advantages are gained from a thicker oil are purely speculation at this point , as i am sure Honda has tried them , and came to the conclusion that the recommend viscosity is sufficient for most every circumstance you would encounter while riding
Hopefully between the 2 of us that gave you more insight as to what to do......
If not , then ask away......