Kind of like asking what oil to use....... a big can of worms.
I will chime in and say after running a VTR for close to 19yrs now I believe the stock gearing is the best to use on these bikes.
If you must re gear then go no more that +2 on the rear or -1 on the front. Any lower than that and you are just going backwards in my opinion.
Loud pipes don't save lives, knowing how to ride your bike will save your life.
standard here too............. If I need it to be lively I keep it in 5th, and when I am hammering on I still end up looking for 7th gear, so I never feel it is over geared
I used to run 16/43 gearing for many years, but like others have said have gone back to standard gearing 16/41, but it is all down to personal choice, what suits one may not suit another,
Depends on your riding style, usage and engine or other tuning.
If you do lots of motorway miles lowering the gearing doesn't help.
I found, with a lighter flywheel, cans and a filter down one on the front was nice,
but as I added more power with engine work I was able to return to std gearing but kept the same urgency.
It's not falling off, it's an upgrade opportunity.