I'd go by the temperature chart and weight oil recommended.
For most warm climates, 10W40 is fine for street.
It's not necessarily the weight of the oil, it's also the other ingredients/additives that enhance the quality of the oil.
Especially for bikes which use wet clutches and share oil with engine and gearbox.
Back in '04, a magazine had an issue where the tested several brands/weights of oil, both petroleum and synthetic.
One very interesting test was to try and de-bunk the myth of synthetic oil having less friction.
They took a stock Yamaha R1 and Suzuki GSXR1000 and dyno'd them with 10W40 petroleum oil. Then drained and filled with 10W40 synthetic, then re-ran.
To their surprise, both bikes showed an increase of HP across the entire rev range with peak HP increase of about 3.3 HP at 12500 RPM. Just from oil.
Now that wasn't 3.3 HP over the entire rev range of course, but there was a measurable difference from at least 2000 RPM.