IIUC, the X1 is the "business-lite" line - the T4XXs are the ultrabooks with ethernet, docking ports, and (at least on my T431s) a VGA port. They've just decid

IIUC, the X1 is the "business-lite" line - the T4XXs are the ultrabooks with ethernet, docking ports, and (at least on my T431s) a VGA port. They've just decided there's a market segment that prefers a thinner laptop without an ethernet port.