There are two competing priorities:
1/. Bright enough to see on a sunny day
2/. not so bright as to be blinding at night.
in my opinion the stock bulbs are plenty bright enough, if you need more cues to remind you to turn off the blinkers, fit a beeper. My RS has such a device stock and I miss it on the R65 - by pure chance my wife's R65/80 had one fitted new (1979 edition) and it is still on the bike, albeit disconnected......A plot is beginning to form.