I remember the SWA videos done for earlier versions of SONAR, I really could not bear listening to that accent of the guy who did them for long, though the narrator was knowledgable. Karl Rose is a significant improvement over that guys accent, yet still has a foreign accent that make it not as comfortable as listening to a non-foreign accent, for me. And some days, listening to a foreign accent for long periods of time is no problem.
I guess one can get weary of a certain voice, so it's good to have different choices made available.
Still, me being American and used to North American accent voices, I don't think I could ever grow weary of a North American accent voice such as Eli's or Craig Anderton's, or Bill Edstrom's. I mean, I went through college with lot's of lectures and never grew tired of hearing a North American accent voice, though some of the lectures were boring, I can listen for hours at a time and for days, and feel right at home with it. But I can grow tired of hearing a voice with a non North American accent to where it impairs my learning from the source video/tutorial.
Yet, I reckon to suite the most users, providing tutorials/videos done by a variety of narrators with various approaches to how to do things is the best approach. And the value of reading material for learning purposes becomes apparent in this situation.

I do prefer video for learning DAW software related stuff, though.