It's not about the White Primer Crusaders being better, or the Cult of the Black Primer being right... it's about all those idiots using grey primer being totally wrong.
More seriously... It all depends on your personal preferences, techniques and materials. It has little to do with end results or time.
I've used white, grey, black and brown primers over the years. I started on white & used it for a long time. But for the past 10-12 years (at least?) I've been using black primer for 90+% of my painting, with brown coming in second place and white & grey almost never used.
I'm a layering & wet blending guy, I hate washes and glazes. I always work from the "inside out" and always work from dark to light. Anyone who wants to argue about bright colors and black primer can go look at my plog first
before coming back here and debating the issue.
Black primer works for me. It might not work for everyone else. That's OK. There's no real right or wrong. I mean, it's not a "black & white issue," right?
Use what works for you, your techniques and your paints.