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.