I have not done blind tests, but I don't really feel the need to. Enzymes work best at different temperatures and a 150F rest isn't doing the best for beta and alpha enzymes. Separate rests are best. But I guess if you don't care to spend a little extra time then don't. That's why this hobby is great, we can put into it what we want to get out of it.
A 150F rest isn't doing the best what? Separate rests are best at what? Why?
I get that the enzymes do different things, but none work in a vacuum. Why is it better to have alpha and beta active separately, rather than together? And how are you sure that alpha isn't having a significant effect down at beta rest range before you ramp up? Modern malts have a crap-ton of enzymatic activity, and even if it's at a lower rate there's a good chance that alpha-amylase is still gobbling away well enough just by sheer enzymatic content at beta rest temps. And frankly, alpha amylase activity will certainly improve beta amylase's effectiveness, by exposing more 1-4 bonds for beta to act on.
I think you have to be really cautious to start extrapolating scientific facts, given how complex the chemistry of wort and beer production is. You can make all the claims you want, but they are really just unproven hypotheses until you back it up with data.
I have to agree on Eric's point about the complex dynamic nature of the mash, especially with high DP malts. We like to compartmentalize and simplify things, but that's only happening on paper for our linear ability to consciously think of one thing at a time. To consciously think of the mash in reality would sound like a room full of people all talking at the same time. In studying Troester's work, the part of decoction that made sense was the breaking down of more starch trapped in matrix, and then introducing those starches back to a now hotter mash so they can be converted to long chain sugars. You convert short chain in a beta rest, then decotion, then convert the new exposed starches to long chain. But I'm not very convinced that its happening very effectively, if at all, in a step mash where trapped starches aren't really exposed to the rigors of boiling and stiring.
Personally, im not experiencing much difference in my single infusion mashes between 148-152. I need to be up around 156 before I see a distinct measurable change in final gravity. (When I brew two near-identical beers with just mash temps different) I've done a grand total of two step mashes, so Im not an expert, but I didnt find that the high temp A rest did anything for residual sugars/body. Its possible if not likely that I held the B rest too long.
Problem here is body does not equal residual sugars. Most German beers finish at 1.010 or below and they are full bodied. The thing with doing long Beta then a long Alpha rest is you get the attenuation profile and the body profile both together. I find my single infused at 150F lagers to be thin tasting. They should be dry yet full, that's what I feel a step mash, properly executed, does for the beer. But, as Eric said, I'm not wanting to go around purporting things that I can't necessarily back up with all kinds of scientific data.
Also, as was said, you can't really argue with perception. If you taste graham cracker, but I don't and taste bread crust instead, in the same beer...well you can't really argue that.
And I agree, Ken and Jon, doing a complete side-by-side would be a great way to do it. I wish I had the fermentation space for 10 gallons of lager. My fridge doesn't fit 2 buckets.