Simplicity for one 🙂
I have tried AWS S3, Google, Netlify…
The first two are WAY too complicated. Just look at how long the Publii setup pages are. Crazy. Good grief, these are just simple static sites !!!
The biggest downside with Cloudflare that I can see is uploading the static website. It needs to be dome manually from their website (it is fast and easy btw). There is an alternative which is to use a command live uploader that Cloudflare provide but IMO this is too messy.
If Publii had a built in uploaded for Cloudflare, that would be the best.
But still, Publii > ZIP file, then Upload button > wait 5 seconds > DONE is a pretty good option.