Rotax dsc info

I am after some info on the rotax dsc. Is there any difference between barrels that are a cast liner and nikasil other than the coating? And which one is preferred?

Photo of my barrel with nikasil

Do they both have the bridged exhaust port? Nikasil arguably transfers heat better and is a harder material. It’s more of a nuance than anything though.

But if one has an elliptical exhaust port, chances are that’s going to be a tad faster.