Yeah I switched from 15W (2 categories) to 20W (also 2 categories). If I vote for the middle category I'll feel like I didn't really 'upgrade' my light!
I still wonder about 'effective' wattage too. Dyno people will tell you that 6W aimed along the road will give you better vision than 20W aimed through the air, you know not where. That could be true.
And then there's LED or HID 'equivalency'