I don't have any of this experience with GMail. Not saying it doesn't have flaws - but my experience is pretty great.
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.
I now have personal email on Fastmail and work on Google Apps. The difference is quite striking. It'll take a good 20 seconds before all of Gmail is loaded, Fastmail loads in under one second. Gmail will easily take 300-400 MB of RAM in Chrome after a few hours, Fastmail is around 40-50MB.
Then there's clicking on emails. Once you've browsed for emails in Fastmail you'll understand why I thing Gmail is slow these days.
Also Fastmail's IMAP implementation is much more reliable.
Gmail has become bloated enough that it's really only usable on modern hardware. I have an older laptop I use when I travel (don't really care too much if it gets stolen, damaged, etc.) and gmail is painfully sluggish on it while Fastmail is still quite usable.
Fastmail has also, however, become more bloated than it used to be. I preferred their UI from a couple of years ago, but have grown to tolerate the current one.
I think the code to integrate the other Google services is the problem for me - I don't need it and it clutters my experience.