Include me as one of the pro builders that believe frames with thin walled tubing rides better. There are a lot more people with opinions about this than have actually ridden one with 7/4/7 wall thickness in the main triangle. Very few production frames were ever made with tubing that light because of the chance of failure in case some fatty rode one. Raleigh had their Reynolds 753 SBDU made in the late 70's until I don't know when they stopped. I actually watched them being made in the 70's. The workers were building them just like custom frames accept on a bigger scale. Reynolds required builders take a test to be 753 certified. Terry Bill at Reynolds told me when I visited him that up to that time every American builder had failed the test. Anyway my point is that the most likely way someone can even try out a frame that light is if it is custom made. That means it is a pretty small sample size of people that have ever ridden one to compare.
I actually made myself a frame with .6/.3/.6 (Ishiwata 015) and a 1" top tube in 1977. What surprised me was that it was not all that flexible. In fact I didn't particularly notice frame flex at all. I think it was around a 56 + cm frame. I'm 5'8" and fairly light and can pedal smoothly. Over the years I've built many frames for customers with 1" top tubes with 7/4/7 walls. Most of these customers where under 6' with normal (not skinny) weight. Almost always they were complete bicycles so I had a chance to test ride them 1st. I know what this kind of frame rides like. Of course when a customer was taller or heavier I used thicker or larger diameter tubes.
Over the years I've made several frames in the 57 cm range for myself with 1" top tubes and 7/4/7 walls. I don't know how to describe the difference except to say they feel more "lively". I don't have any trouble distinguishing them from frames with 9/6/9 tubing. I can tell immediately by the feel of the ride. Just lately I made a frame for upright riding as an example/demonstration in my framebuilding class. It has a 1" tup tube with 9/6/9 walls. It rides nicely as I expected. My wife rode it and immediately wanted one too. I made hers with an almost identical geometry except with lighter 7/4/7 main tubes. The rear triangle was lighter as well. I was surprised at how much difference the ride qualities of each bicycle is. Again I don't know to describe the difference except to say it was more lively. I don't think the ride quality difference has anything to do with the actually weight difference. I have done other side-by-side frames/bicycles comparisons in the past but I'm not ambitious enough to describe them. And besides that will make this post longer so nobody will want to read about them.
This subject often gets referenced to Jan Heine's preferences and test rides in his Bicycle Quarterly magazine. He came up with the word "planning" (a boating term) to try and describe the difference in ride quality he experienced when riding a light tubed bike. Unfortunately his hypothesis to try and explain the difference always brings up mockery - including some that haven't ridden such a frame. I don't know that I agree with his explanation but what I know from my own experience that - for me - I clearly prefer and can tell the difference in ride quality of a thin walled 1" top tube compared to heavier versions. I have ridden bikes with various tubing sections and know what I like. YMMV.