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.