Can't say I've ever had performance issues or even a moments downtime whilst using gmail since it was launched.
Is a paid vs. free solution even comparable?
It's also a bit weird to compare the requests made on initial load considering these web pages are arguably meant to be kept open- but regardless, shouldn't the browser be caching these?
I think a more fair & thorough comparison would be to investigate what gmail has that other solutions don't by introducing the larger initial overhead. I'm guessing a lot of cross platform compatibility code and plenty of code to integrate to Google's other services.
In which case, I would say if you are concerned about the initial page load and having more responsive interface (once again, no complaints here) and don't need integration to Google's ecosystem, you may not be the target customer for gmail. Which is okay.