Last time I tried mapping only in Roll20, the lag got ridiculous. Went back to MapTool for making maps, but didn't like that I would have to go back and forth if I needed to make changes to the base map. Then I finally realized what I was doing wrong... trying to make the whole map on one page. So now I'm making the map in 20x20 zones, much like an MMO. Which kinda makes sense anyway, since I'm making this for a D&D 4e Hexcrawl campaign.