t3a instances run on AMD EPYC CPUs, depending on your workload (threads, spikes, etc.), you will probably have similar performance if the right pieces match. In general, it seems that the t3 instances running Intel CPUs are usually faster.
You can also get a 10% discount on your EC2 computing bill:
Amazon Web Services (AWS) announces general availability of Amazon EC2
T3a instances. T3a instances are variants of T3 instances and feature
AMD EPYC processors with an all core turbo clock speed of up to 2.5
GHz. T3a instances provide additional options for customers who are
looking to achieve a 10% cost savings on their Amazon EC2 compute
environment for applications with moderate CPU usage that may
experience temporary spikes in use.