Originally Posted by
mosy
Thanks hokiefyd for the detailed response! You make a great point about changing the brakes to Shimano and still coming out $75-100 ahead of the Trek DS3. However, while I agree that the drivetrain is nearly the same, there are some components that are slightly better on the DS3 i.e. Acera levers shifters (instead of Altus on the Roam) and Alivio rear derailleur (instead of Acera on the Roam). Does this not close that $75-100 gap or at least make it much closer?
The Acera and Altus shifters are pretty interchangeable. The Altus ones have the gear display below the bar, and are just labeled "9 1" with nothing in between. The Acera ones have the gear display above the bar, and are labeled "9 7 5 3 1" which I like better. I upgraded my Roam to the Acera shifters only because I found then super cheap on eBay. They are "SL-M3000" if you want to search the internet or eBay for them.
The Acera derailler on the Giant is actually of a newer design than the Alivio derailleur on the Trek. The Acera is an RD-M3000 and uses Shimano's Shadow derailleur technology. Shimano have moved all of their mountain deraillers (M in M3000 means "mountain) to the Shadow design, even down to the Altus level RD-M2000. The Trek's Alivio is an RD-T4000 and is a more traditional derailleur with the sprung B-pivot. In this case, T in T4000 means "trekking", and Shimano have not moved their trekking derailleurs to the Shadow design. In this case, it's really six of one, half a dozen of the other. I've used both types and both types have advantages and disadvantages.
The shifters and derailleurs are so close, they are functionally interchangeable. The one thing you can't change about the bike is the fit and finish and color. If you like the Trek better, then buy the Trek. If you like the Giant better, then buy the Giant. I'd look at components only if it's a true toss-up and you can't decide. What about your bike shops? If the Trek and Giant stores are different, do you prefer one over the other? Staff there? Friendliness? Both Trek and Giant offer excellent warranties, so you should be covered well there.