Homer at the Bat is hilarious, uses guest stars very well, and keeps the focus on Homer, but I'd say there have been better gagfest episodes in the show (although Homer at the Bat is certainly among the best ones).
Last Exit to Springfield is more well-rounded; its humor is on par with, if not better than, Homer at the Bat's humor, both plots are very strong, and the workers singing "they have the plant, but we have the power" in the darkness still gives me the chills every time. It's the clear winner here.