1st--have you looked at Seaworld. com and tried to book thru them--they have GREAT package rates to Marriott residences with Seaworld tickets.
HGVC will be more upscale and have a real kitchen, dining, living room. done in pretty tropical decor. Large open kitchen, well stocked with pots/pans dishes, dining table with 6 chairs, sofa, loveseat and very large TV. 2-3 pools, overlooking lake, fenced, sandy bottom kids play area. King bed in BR, JAcuzzi tub. pull-out sofa. One of the nicest timeshares in ORlando.
Marriott Residence. 1 BR has 2 queens--VERY good ma tresses, pull-out sofa, nice, but generic smaller living room and small dining table with 2 or 4 chairs (very small). OK kitchen in a corner of the room, with a FEW pots, plates, etc. Regular bathroom--potty, sink tub/shower, nice, but no frills. Pool area is very nice, zero entry with little fountains spraying. Breakfast buffet is VERY good and hearty.
HGVC 1 BR is about double the size of the Marriott 1 BR. if you have older kids, maybe HGVC for the space and the larger pool area. We are a family of 5 with 3 smaller kids--either works great for us---they are both top class places--the HGVC are fancier rooms and would be easier to "really" cook in b/c they have more stuff--but to go to SEaworld and reheat leftovers and do minimal cooking/eating, Marriott would be fine.
We are going to MArriot again for Christmas.