They all load the same and have the same programs live-wire has a digital gauges built in, So if you already have analog guages buy the xcal.
The cheapest place new is any of our vendors, If you are going to do custom tunes in the future I would buy the SCT from some one whom does the custom tunes(DJ's Innovation) ect. But you do not have to.
I got my Xcal 2 form a Friend who bought a 6.4 and Vivian will still custom tune it.
Good Luck