the Jasper MoBo (read that motherboard): new 65nm CPU and new 65nm GPU
basicaly a new revised version of, you could say, the console which is less prone to RRoD problems. I don't know how much more reliable it is, but I haven't heard anything bad about it yet, so it must be that good. (mine is a Falcon 😬 )
there are ways to know which MoBo you got (though most involved opening the console 😐 ). The safest way would be to look at the "manufacture date" you can see it in the back of the console, around the serial number. Anything (be it arcade, pro or elite) that says
"April 2009"or later should get you a Jasper Xbox.
the Pro version its the safest choice, but the Arcade one should be most appealing for it's price tag, but you will suffer without an HDD