We just love HTC's One X here at Engadget -- it's quite possibly our favorite smartphone of 2012. Three devices have crossed our desks over the past year -- the original with HSPA+, AT&T's model with LTE and, more recently, the global One X+ with HSPA+. Now the saga continues with AT&T selling its own version of the One X+ with LTE on board. What's different between these handse
