I think 4k will always look better downsampled to 1080p than 720p, simply because it is an exact multiple of 1080p. The poll has no options for a PS4 Pro running in 1080p DS'd to 720p, or running in 4k & DS'd to 1080p or 720p. All of which would produce differing results. If the PS4 Pro was running at 4k & was downsampled to 720p, there would be less aliasing compared to a standard PS4 running at 1080p on a 1080p TV. Whether it would look any better or not would be subjective, & down to many more factors than just aliasing.
EDIT: Also, I have a 10 year old budget 720p TV & am really happy with it. It has a great looking picture, & I've never noticed any problems with lag (if there is any it's not discernible). I've used my PS3 & PS4 on it without any problems for several years now.