We've been to both multiple times with our three boys, and I would definitely recommend Garden Grill. It's our boys' favorite restaurant and our arrival night tradition.
Food: We were just there in July again, and we think the food has improved significantly. We previously said the the food was good and character interaction was great - now I'd say both are great. Our boys weren't fans of the new sweet potato fries, either (I loved them!) but they still brought out the mac and cheese and our boys loved that. Someone reported that you can ask for nuggets and regular fries - but even our pickiest eater (and he's VERY picky) liked the drumsticks and mac and cheese enough that he didn't want to ask for the nuggets and regular fries.
Characters: Best character interaction of any character meal we've ever done. All three of our boys love characters, and they spend a lot of time with our kids - we usually see each character at least twice per meal. But we always like to start our kids with this meal because if they didn't react well to the characters, they would not see them constantly like you do at Chef Mickey's. At Garden Grill, you can request a booth on the lower level - the booths are high so that little ones only see characters when they are at your table. If a child doesn't react well, you can just tell your server and the characters will pass you by. And if your kids love the characters (like ours do) they can only see the characters when they are at our table, so they actually eat something in between character visits.
Set up: We love family style (like at Garden Grill) instead of buffets (like at Chef Mickey's.) I think the food quality tends to be higher, and it's really nice to sit down and have the food and the characters come to us. Also, we don't have to worry about missing characters when they come around. The whole atmosphere is just so much more relaxed at Garden Grill, and our boys love to see the different scenes in the land ride as the restaurant rotates slowly.
For our next trip, we were going to make ADRs for both Garden Grill and Chef Mickey's, but our oldest son suggested we skip Chef Mickey's and our other boys agreed.