What's the difference between 2-row and 6-row malt?
I've been brewing all-grain for several years, but have been using recipes and kits. I'm starting to develop my own recipes, using the process outlined in "Designing Great Beers" by Ray Daniels, but it's not clear to me what the difference is between 2-row and 6-row base malt. When should I use one vs. the other? What are the advantages or disadvantages of each?