I do net.
When I'm in weight loss mode, I track my calories and, when unsure of them, I overestimate. I also track workout sessions that aren't a regular part of my daily activities (i.e., I don't count most walks unless they're brisk and over 20 minutes; I do count every time I use an exercise dvd even if it's only for 10 minutes). With exercise, I always underestimate my calories burned, sometimes deliberately and substantially.
Then I keep those exercise calories in a bank, sort of like the way I understand WW to use flex points.
I aim to keep to about 1400 calories a day, but there are some days when I'm truly not that hungry, so I eat 100 or so fewer. Those go in the bank. Then there are some days when I'm hungrier or am doing something social that adds in calories. On those days, I use my "banked" calories.
This might sound kinda complicated and accountant-like
, but it ends up happening pretty naturally. Using this system, when I look back over my week's calories, they end up being around 1400 net calories. They may be slightly less because of how I underestimate exercise and overestimate food.