I have a 1.83 GHz MacBook Pro with 1 gb of RAM, and a friend at school has a MacBook with 1 gb of RAM and a 1.83 GHz Core Duo. My MacBook Pro just feels snappier and generally screams in comparison to the MacBook which just feels very very fast.
That is odd. It shouldn't be a 'night and day' difference. He might want to check if he has any programs running in the background that are using up a lot of RAM. (Some printer/scanner software that is running in Rosetta, for example.)
I heard from an Apple engineer that the MacBook Pro's logic board has higher bandwidth for pretty much everything and the MacBook Pro's components are generally higher quality, kind of makes sense with the price difference...
Nope, sorry. Same bandwidth from processor to chipset, same from chipset to memory, same from chipset to hard drive, USB, FireWire, everything. The *ONLY* difference is the video. And, ironically, the integrated graphics actually would have slightly FASTER access to the chipset (since it's part of the chipset, it has lower latency,) but slower memory, since it shares the main memory bandwidth with the processor, whereas the MacBook Pro's dedicated chip has its own dedicated (and faster than main system) memory.
I have to weigh in that as others have said, unless you are going to play the latest 3D games, use Aperture, or Motion, you won't really notice the difference.
But for $100, I'd go with the Pro, for sure. Not only do you get the discrete graphics, but you get the ExpressCard slot (I use a memory card reader in mine,) and a 15" 1440x900 screen instead of a 13" 1280x800 screen. Unless you REALLY want the smaller physical size, go for Pro.