I've had two Truths, one Id ( for 5 years) and now the Moment for the past three years.
If the ID has a Float on it ( 2" travel) Vs any of the longer shocks with 2.25" travel, the bottom bracket will be a little lower and handling will be a little more stable in slow speed tech trails and more stable on faster downhills. With the standard longer shock, steep down hills are more difficult.
Keep in mind, getting any kind of warranty help on a used EW frame will be very difficult ( Yes, like all brands, EW have been known to break, in cluding three of mine)
Having said that, EW bikes ride better than anything I have every tried and I've ridden just about everything I can.
The cheaper and safer thing to do is go buy a Specialized Pitch or a Giant Trance X. A little more weight won't kill him.