Disclaimer: I have not used either product; I have used a number of Cloudflare's (mostly free tier) offerings.

In addition to the other points brought up, it looks like pricing strongly favors Bunny once you're outside of Cloudflare's free tier.

Per billion rows read: Bunny $0.30, Cloudflare $1.00 (first 25B/month free)

Per million rows written: Bunny $0.30, Cloudflare $1.00 (first 50M/month free)

Per GB stored: Bunny $0.10/region, Cloudflare $0.75 (5GB free)

Bunny also has a lot better region selection, 41 available vs. Cloudflare's 6 (see https://developers.cloudflare.com/d1/configuration/data-loca...). Even though Bunny charges storage per region used where Cloudflare doesn't, Bunny still comes out cheaper with 7 regions selected. Bunny lets you choose how many and which regions to replicate across; Cloudflare's region replication is an on/off toggle that is in beta and requires you to use "the new Sessions API" (I don't know what this entails).

The main reason I haven't tried out D1 is that it locks you into using Workers to access the database. Bunny says they have an HTTP API.

I plan to stick with VPSes for compute and storage, but I do like seeing someone (other than Amazon) challenge Cloudflare on their huge array of fun toys for devs to play with.