I think with the risk that comes with Poly Standard View right now in terms of possibly being in a room overlooking the Poly Tower construction site, I would lean GDT. If that risk doesn’t bother you then no worries, just something to keep in mind.
Poly certainly has locational advantages to visit other resorts and watch nighttime MK fireworks, but doesn’t have the most impressive or interesting holiday decorations itself, in my humble opinion. I’m a Poly fan all day long but the holiday background music they play around the grounds is one of my least favorite things ever.
GDT is beautiful and especially around the holidays. We stayed there over Thanksgiving a couple of years ago and felt it was a perfect place to get in the spirit of the season. Obviously it’s bus or vehicle only from there but it’s manageable with proper expectations. CSR is actually pretty central to most WDW things so no trip is overly complicated.
Several pros/cons, but I think I would lean GDT