Always a bit of a gamble trying somewhere new for 8 nights. If for some reason it's not suiting you, then you're stuck!
On some level, we have to remember while the Island Tower seems like a big deal in our little corner of the world, outside of Disney sites and the blogger/vlogger community, do people really care all that much? Many probably probably say "it's DVC" and move along without much thought.
But no doubt you're still in the holiday zone and then marathon weekend creeps in (Floridian Way will be closed in one direction the morning you leave, in case you didn't know that). On some level I suspect the normal Poly vibes will still be the case - which to me is a combination of both a busy resort (Great Ceremonial House, dole whip lines, monorail lines) and an overall chill vibe (the grounds, rooms).
From the looks of it I could get pretty cozy for 8 days in a 1BR TPV room. The rooms remind me a bit of the Tonga suites in both style and quality, and space.
If this were me the chance to try something in the opening days (and a place where cash stays will become more difficult over time) would probably win out.
But tough call if you've got a specific definition of "relaxing" you're trying to find in your choice.