Wow, that's a somewhat difficult comparison. It's because they have pretty similar components but still different. First, for the Giant Roam 1, it depends on the year. 2012 is Shimano and 2011 is Sram. I'm not familliar enough with the Sram quality levels.
But, let's start this for the fun of it. haha. The Trek 8.3 DS has an Altus front derailleur while the 2011 Giant Roam 1 has an Acera which is superior. At the same time, some people say the front derailleur is not as crucial as the rear derailleur. One win for the Giant Roam 1.
The Trek 8.3 DS has a 48/38/28 crankset and 11-32T cassette while the Giant Roam 1 has a 48/36/26 and 11-34T cassette. I find a 36T middle chainring is more comfortable for a hilly area like mine so I would prefer that. And the 34T cog gets you a lower gear for climbing hills. Here, I'd want to give the win to the Giant Roam 1.
The Trek 8.3 DS has 700x38 tires while the Giant Roam 1 has 700x40 tires. For more cushy tires, the Giant Roam 1 wins again.
The Giant Roam 1 also has sealed hubs. Well, there's always the sealed vs. serviceable debate here but for a bike capable of going on trails, I'd give the win to the Giant Roam 1.
However, the Trek 8.3 DS has an 8 speed Acera drivetrain. If you wanted to go with friction shifting with Falcon shifters for example, I think 8 speeds would be more realistic because some people find friction shifting more finicky with 9 speeds.
Other than that, I'd give the nod to the Giant Roam 1 but since I'd prefer friction shifting to avoid having to have the derailleurs adjusted more often, I'd almost feel tempted to change the derailleurs and shifters to Deore. But, some people find Acera acceptable, just that if you can't adjust derailleurs easilly like me, you'd have to go to a shop once in a while to get them adjusted. Some stores offer free tune-ups though.
Other than that, as for the brakes I'm not sure if there's a major difference. Same thing for the frame geometry because one gives top tube length and the other effective top tube.
EDIT: I just noticed the Giant Roam 1 doesn't have a chainguard however.
Also, some people prefer Sram cassettes and KMC chains. The Giant Roam 1 has a Sram cassette and KMC chain but the Trek 8.3 DS has a Shimano cassette and the chain is not listed.
Last edited by hybridbkrdr; 10-03-11 at 08:43 AM.