What scale is right for your next project? That depends on the subject of your model, and what characteristics you find most important. Some of us are "constant scale" builders - we build all our models to a single scale, sometimes regardless of the subject. This allows easy size comparisons and lets us combine several models in a diorama. (It also reduces the time you spend browsing at the hobby shop, but you'll have to decide for yourself if that's an advantage.)