Lunch is quick service for breakfast and lunch. You pay for what you order (so you can split entrees, or order a kid's meal for an adult, or just order some soup or a cupcake if that's what you want to do). You can pre-order food online ahead of time or order at a kiosk when you arrive for your reservation. At lunch you also get your own drinks, utensils, napkins, etc. CM's bring your food and clear your table but otherwise it is like any other QS meal. Price is much less than dinner, food is good.
Dinner is a table service, prix fixe meal. Everyone pays the adult price or the child price (3 and over) regardless of what they order/ eat. You are seated (do not choose where to sit), and your food/ utensils/ beverages/ etc are all served to you like any other table service. Beast is there for a photo, but there are no other characters.
I overwhelmingly prefer lunch to dinner. It's the same castle (so same atmosphere as any other meal), my food comes to me (it's fun- you order, choose a seat, and your food "finds" you), I don't have to clear my table. So basically it's a little more service than a traditional quick service all while sitting where I choose, eating at a pace I prefer (my toddler can take an hour to eat a sandwich or inhale a plateful of food in 10 minutes), and not spending a set price (or 2 TS credits) on a dinner where my 11 yo would rather have a cheeseburger and I can't finish my $55 meal.