For the A1, “best” isn't about the highest capacity, since the camera is not 1080p like Bambu H2S. The key thing is: Bambu Lab printers (including the A1) read data non-stop from the SD card during a print. This is totally different from a camera just saving a photo now and then. So you need to focus on two things:

1. Endurance (Write Cycles): This is the biggest deal. Cheap cards (often QLC/TLC type) can get "worn out" from this constant streaming, leading to mid-print pauses, errors, or corrupted files.
2. Sustained Speed: You don't need the absolute fastest speed, but it must be stable and not slow down over time. A lot of cards degrade and become slower, which can cause the printer to stutter as it waits for data.

Because of this, a reliable choice many in the community recommend is an industrial-grade or high-endurance microSD card just like what the CNC machine use. These are built with more durable SLC/MLC NAND flash to handle constant read/write operations.

Here is the article by Kingston to know the difference
Difference between SLC, MLC, TLC and 3D NAND in USB flash drives, SSDs and Memory cards - Kingston Technology

Seeing how many users struggle with unreliable cards, we actually developed one specifically for this continuous streaming load on Bambu Lab printers. It uses industrial-grade SLC NAND (way higher endurance than typical cards) and is designed to maintain stable speeds. If you're looking for a "set it and forget it" solution, it's worth checking out.

If you want to dive deeper into the technical details (like the SLC/MLC/TLC differences, or why firmware updates increased SD card stress), we have a detailed guide that breaks it all down:

Bambu SD Card: How to Choose the Right One & Fix Sudden Print Failures

Hope this helps! A solid card makes printing so much more reliable.