These are both two of our go-to's so it's hard for me to say one over the other especially if the same price but maybe I can give you the rundown of what we like about each so that you can make a (hopefully) more informed decision.
Tropicana: price & location are the best things about this hotel. After that there isn't much but I cannot stress enough about how great their close location is. They are also close to a McD's which gives a cheap & fast food option. Fair warning they do have some more rundown rooms & I have had family be very disappointed in their stay there because of that. And also, the staff isn't the friendliest. Not that they are unfriendly just that they don't go out of their way to be helpful, cheerful. Except the valet/parking guys, they have always been awesome.
Sheraton: nicer amenities & the convenient CVS almost next door. The walk is definitely longer which isn't bad in the morning but can be brutal coming back. There is the toy story parking lot across the street & you are able to use the free shuttles to the park even if not parking there but we always have a stroller and usually (esp on the way back) sleeping kids in it so hoofing is easier in that case. If you will be spending any significant amount of time in your hotel this is the better choice as the rooms, pool & hotel feel in general are much nicer. The beds are more comfortable & they have historic Disney photographs throughout the halls so it gives it just a touch of a Disney feel (nothing like that at Tropicana). If you are an SPG member there are some other perks at Sheraton that make it one of our favorites but not sure if that applies to you. In case it does, if you are a gold member you can check in as early as 7am (subject to availability) & check out as late as 4pm (again subject to abailability). This perk allows us to get extra park time & maximize our trips without having to pay for another hotel night. Lastly, we in the past have used points to upgrade to club level which has been awesome with free hot & good solid breakfast as well as appetizers at night along with unlimited free soda & water from the lounge.
Overall you can't go wrong & hope you have a fantastic trip either way!! And happy bday for your DD!! Make sure to get a birthday button for her big day!!