I prefer planting everything I can from seed but there are some advantages to using plants. Eggplant sprouts, in my garden tend to get killed by flee beetles whereas the bigger plants can handle more damage. Plants can be mulched immediately so that I don't have to weed again. I have had success planting kale and mustard greens from seed but little success planting broccoli or cabbage.
All this being said, the real reason I set out plants instead of seeds is that I just didn't get around to it. The cold and snow kind of took my motivation away.