Is it really "admin account vs. guest account" or is it "lived-in account vs. clean account"? Try creating a new, clean admin account, and before you go customizing settings or installing anything, see if the lag happens or not.
If the lag doesn't happen on a new, clean admin account, then you can start looking at what's different in your "lived-in" admin account vs. a clean account. Maybe you've installed Application Enhancer or SIMBL or other Input Manager hacks that are screwing up your performance. Maybe you always leave an email client or web browser running in the background on your lived-in account, but you didn't do that on the new clean account.
If the lag still happens on a new, clean admin account, then you can test the "admin vs. non-admin" hypothesis by creating a new, clean non-admin account (really create an account, don't just use the guest account). Then see if you get the lag there.
I strongly suspect that the real difference is a lived-in account vs. a new, clean account. Although it might not come down to settings differences as much as how your behavior patterns are different on your lived-in account than a new clean account (like you're more likely to have more apps open in the background on your lived-in account).