DB access speeds, App(linux)<->PG(linux) vs App(linux) <->MSSql(Windows)

Hi:  I'm trying to get a 10,000 ft understanding of the difference in DB access speeds for two different scenarios...

Scenario 1:     Apps are on linux.  PG DB is on linux (different server than apps)

Scenario 2:     Apps are on linux.  MSSql DB is on Windows (obviously a different server)

The apps are typically perl scripts using Perl DBI. 

I'm thinking that since perl has a DBD driver for PG, that would be faster than going through ODBC to get to the MsSQL DB, but I'm not sure about that.

Any insights/guesses ?

Thanks in Advance.