Should I buy the Canon RF 28mm or a used EF 24mm pancake?

If you’re using a modern Canon EOS R-series mirrorless camera, I’d generally lean toward the Canon RF 28mm f/2.8 STM for most people.

Why: it mounts natively, so you keep a compact setup without needing an adapter. The EF 24mm pancake is wider, which is nice for landscapes, interiors, and architecture, but on an RF body you’ll need an EF-EOS R adapter, so the overall kit will be less compact than a native RF lens.

The focal-length difference matters too:

• 28mm: a little more natural and flexible for everyday shooting, street, and casual people photos.
• 24mm: noticeably wider, which is great when you want more scene in the frame, but it can exaggerate faces more if you shoot close.

So the short version is:

• Buy the RF 28mm if you want the smallest, simplest option for an RF mirrorless body and you’re okay with 28mm.
• Buy the used EF 24mm pancake if you specifically want the wider 24mm view and don’t mind using an adapter.

If you’re on a Canon DSLR, skip the RF lens entirely — it won’t mount natively, so the EF 24mm is the practical choice there.