<< The Explorer is much larger, looks better (IMHO) and also has a couple extra buttons on the side. >>
I think you're confusing the standard Microsoft Optical mouse (it's just like the old IntelliMouse ball mouse, except for the IntelliEye) with the newer IntelliMouse Optical, which is a symmetrical mouse with "back/forward" programmable buttons on both sides (good for both righties and lefties; this was a big problem with the Explorer, a mouse designed only for right-handed users). I got my Explorer mouse as a Christmas gift year last year (one of the toys on my list, hehe) and I'm loving it, but I'm wishing that I would have waited for the IntelliMouse Optical (it's $20 cheaper and a lot more comfortable IMHO).
<< The wires on the older ones seem to short out quick (mine within a month). >>
I've seen several people with the wire problem on older Explorer mice. But according to a lot of them, they got virtually hassle-free replacements (one area that Microsoft seems to excel in is RMA policies). I haven't had any problems with mine yet after about a year and it's still going strong. Worry not though because by now, all of the old versions shouldn't even be on retail shelves anymore. Just look for the ones with that sticker that says "improved optical technology." That's the "new" one.