My Gmail account is getting pretty full - around 78%. I could either delete some old messages and large attachments, or upgrade to the $50/year version. It's also getting really slow - both to load, and to search messages. I'd be more inclined to pay the $50/year if it made it faster, too - but I didn't see this mentioned on the comparison page and didn't have much luck finding the answer with google. Thanks!
The only way I can see this being possible is if (1) they moved you to faster servers when you bought a business account or (2) they somehow limit the data rate to free customers but remove or raise the limit for business customers. Both seem fairly unlikely for Google.
short version:
Don't upgrade just for speed. i don't see a difference, have never heard of a difference in <i>performance.</i><p>long version:<p>I use both. In my experience there is no difference in performance.
Very occasionally a bug that hits one will not hit the other (but not always).
Also, they get features at different rates. The consumer Google applications get new features and makeovers faster, and then it gets rolled into Google Apps.<p>It sounds like you looked at the feature matrix and know the main differences.
Basically Google Apps gets you a throat to choke (there is support), and access to more API's to do stuff programatically.
If you're just one account, a lot of that value can't be realized.
FWIW, I have both a free account and a paid account, and have noticed that both have slowed down quite a bit in the last few months. Most likely their business is growing fast and capacity management is complicated (even if you're Google)