I dont think you could go wrong with either one really. The only notable hardware difference is Trek's IsoZone frame (which may be good or bad depending on your point of view). The geometries are quite different though so I would shop more on which fit and posture suits you best rather than dwelling on component specs.
All else being equal the Roam series are a little shorter in the reach giving a slightly upright ride, the so called fitness posture. The 2013/2014 DS on the other hand puts you somewhere between that and a true Cross Country MTB posture (the 2012s, which are somewhat sought after now, were even closer to their 29ers in terms of geometry).
Last edited by Sunsanvil; 06-12-14 at 05:36 AM.