I posted earlier that I thought .1 volt settings are more precise.
I always wonder why no one (that I have seen) mentions the lack of precision in .5 watt increments. You can get more precise adjustments on most VV devices, but it depends on the resistance of the head you're using:
If you are using a low resistance (let's say 2 ohm) head, going from 3.7V to 3.8V increases the wattage by .4 each .1 volt.
On a 3.0 ohm head in the same wattage range, going from 4.5V from 4.6V increases the wattage by .3 watts.
Is this important? Probably to some, probably not to others, but it's worth mentioning. The more precise adjustments are one of the main reasons to use SR heads on VV devices.