Andy_K 

Yeah, I did see that article. I'd love to see something with a table showing more details about things like tubing and components for the winning bikes, but I guess the tubing information isn't necessarily available. For instance, I think Pedro Delgado's bike in 1988 was sometimes reported as being a Pinarello Montello, but as the article mentioned it was actually custom-built by TVT so who knows what tubing they might have used. I know when Eddy Merckx was racing he had a lot of input on the builds of his bikes, and I would guess this is true of most top riders. The paint and decals say what the sponsors want them to say, but the rider might convince the team to do something else with the build. And, of course, they might use different bikes on different stages.

Regarding the use of Reynolds 531 by Peugeot and Gitane, it's also worth noting that those would have been the metric-sized Reynolds 531 tubes. I would expect that makes at least a minor difference, but it's mostly just prevailing national preference. I have a Stella that used metric-sized Columbus tubing. You don't see many of those. I think I said before in this thread that it's a fairly good generalization to say that English and French builders used Reynolds tubing (the Stella not withstanding) while Italian builders used Columbus. I've seen it suggested that this is a carryover from WW2 allegiances. Regardless, I think it's more of a cultural norm than a reflection of the builder's assessment of the relative quality.

Before the mid-80's when you were basically choosing between Columbus SL and Reynolds 531, these two framesets very similar weights. It's also worth taking note of the fact that SLX was introduced as an upgrade over SL but it was slightly heavier. Weight isn't everything.