For the workloads I manage, the AMD instances are the same or slower per $ than comparable Intel instance families (m5/m5a and r5/r5a). Those use the 1st gen Epyc AFIK

Regardles, when third generation epyc Milan rolls out to AWS this year or next, the wave of movement to AMD will be massive

For c5a in us-east-1, it's simply not offered in all the AZs we've been assigned