Use OpenSSL's speed command to benchmark the two types and compare results. Here's an example command to run on the server to compare only the key types and sizes you mention:

openssl speed rsa2048 rsa4096

For reference, here are some benchmark results from a modest VPS:

                  sign    verify    sign/s verify/s
rsa 2048 bits 0.000685s 0.000032s   1459.1  31629.7
rsa 4096 bits 0.007574s 0.000113s    132.0   8851.0

As you can see, doubling the certificate key size places an enormous additional burden on the server's CPU and is many times slower. Avoid 4096 bit keys unless you have a specific threat model which requires their use.

Use OpenSSL's speed command to benchmark the two types and compare results. Here's an example command to run on the server to compare only the key types and sizes you mention:

openssl speed rsa2048 rsa4096

For reference, here are some benchmark results from a modest VPS:

                  sign    verify    sign/s verify/s
rsa 2048 bits 0.000685s 0.000032s   1459.1  31629.7
rsa 4096 bits 0.007574s 0.000113s    132.0   8851.0

As you can see, doubling the certificate key size places an enormous additional burden on the server's CPU and is many times slower. Avoid 4096 bit keys unless you have a specific threat model which requires their use.