Even if you used the same decoder in each, it's likely one would still run a little faster than the other, so the CV settings would be slightly different.
No, not necessary. You adjust CVs in each to match them. Manufacturers use different schemes to manipulate speed, which can be a little confusing, but once you understand how this works with each, you adjust them to suit your needs.
Of course, it's often easier to use the same decoder.
Mike Lehman
Urbana, IL
Here's a question that's probably been asked before: if you have two locos that are same manufacturer and model (Atlas N scale Dash8-40 BW) do you have to use the same model decoder in each in order speed match them and consist them? Thanks.