There are some cheaper SSL certificates out there. Would a certificate from Verisign perform better/faster than a certificate from a discount provider?
My gut is telling me that it does not make a difference b/c ultimately the certificate is installed on the server.
From my experience it doesn't make any difference. They all generally use the same set of algorithms behind the scene for the encryption of the traffic and thus it is the implmentation of those algorithms that are more likely to make a difference.
The only consideration I would make would be if the client machines have the Certifying authorities certificate installed. This generally leads to Verisign or a large one being chosen but that was a few years ago now, I believe the coverage is now a lot better.
You might check out this information from IBM. They looked at several different cipher suites with regards to SSL and measured the relative performance of each.
Note that the MD5 algorithm is pretty much broken and useless (also here) when trying to secure anything. So stay away from it.