Good promo for Fastly! Fastly is a great company - effectively they're Varnish-as-a-Service, which is really a non-trivial SaaS. I hope this brings in some business for them.
I've used both and wish Fastly had a mode where a higher level specification could be used for most/simple cases. It's been quite a while since I've used it so may be a capability it has since added.
I feel like Cloudflare is becoming more of a cloud computing platform with a focus on global "instant" delivery of services than a CDN company.
Of course, they're also a really competent CDN company, but they're really leveraging all their experience in that domain to bolster up their compute offerings.
Fastly == Linux (ability to changes lots of things to tailor to your exact needs)
Cloudflare == macOS (prepackaged to work for most general users, limited config)