We did both of these room types (we'll, vgf was standard but that's kinda a wash for these talking points) in our littles first year. We didn't have much of an issue with getting to or from any park in either case, nut the BLT walk is definitely a couple of minutes shorter. I thought the grounds at vgf we're more kid friendly although when we were there, the kids pool was closed (she was 4 months then, so it didn't really matter for us).
Purely based on resorts, I'd probably give a nod to the grand because the lobby, the dining (young kid means sometimes eating at the resort during sleep/naps, and BLT had limited quick service/takeaway options), the grounds, the walk path to poly, and all this made it good for stroller time and toddling around. If you really care about fireworks, then you can't beat BLT theme park view and especially at this age, you just won't get that same experience from a vgf room.
Not sure this helps or hurts, but regardless I think you're picking right by having at least one park with walking access and you will do fine either way.