Please look at my post again, I updated it.
The i5 is faster, but its not an incredible increase for everyday use (you might notice its only a few seconds faster than the i3 UNLESS you are using a single core program. With a single core program, it will shut down one of the two cores, and increase that speed to 3.8ghz
Mhz is just the speed of a processor. There is a .4Ghz increase, or 400mhz.
3.2ghz = 3200mhz
3.6ghz = 3600mhz
**Okay, so if they are shipped from California, does it matter if it was shipped to the Apple Store or your house?