It depends on what the build process looks like, but I find buildx to be really, really slow–and that can be costly if you're paying for the compute time to do that. (The slow part is if you have to do any compiling for the non-native platform on your host. I have tested this doing x86 compilation on an M1 system, and Arm complication on an x86 system.)

AWS has a guide for using CodeBuild where you split the work to build each Docker image using the platform of its target, and then create a manifest at the end.

https://aws.amazon.com/blogs/devops/creating-multi-architect...

I also took a similar approach using CircleCI. A multi-arch build can take 5 minutes using parallel, native builds instead of 45+ minutes (it actually timed out).

Pros: way faster and cheaper builds if you have to pay for the compute time Cons: a much more complicated setup