Did you develop any options about what made the difference in site speed between the platforms? Page size, better asset packing, cdn choices, or something else?
Mostly it comes down to the number of requests and the amount of soul sucking tracking/javascript that runs before the page renders fully. Wix is a particularly bad actor here.
Part one was quite popular on HN. This chapter focuses on website builders that are used heavily by small businesses - Squarespace, Wix, Weebly, GoDaddy, etc. How fast are they? Which websites tend to rank well on Google? Also found a great Google bug. I'll be checking this thread to answer questions, naturally.