It kind of depends. If the tutorial rehashes the "sketch, lineart, color" or "sketch, greyscale, color" recipe it doesn't help much. If the speedpaint is basically just showing the "sketch, lineart/greyscale, color" it's not terribly helpful either. There are TONS of both around already. xD What makes either one good is what goes beyond that. Actual art theory and how it's applied, the thought process behind the composition (guiding the eye, positioning, etc.), choice of lighting and how it's applied (why light from the back? why does the material look the way it does here? why blue light?), how the artist came up with the design, thought processes...

Blah sorry for rambling xD I hope it helps. If you decide to do either that's very generous of you, and I thank you in advance!