Perhaps a better way of thinking about it would be lighter-heavier, rather than best-worst. I say that because the main and most important difference between the cheaper and more expensive steel tubesets is that the UTS and Yield Strength increase when you spend more. That means that the stronger and more expensive tubesets can have a thinner wall, and so they result in lighter frames and forks. The alternative is that the tube thickness remains the same, but the frameset becomes much stiffer and stronger, which might be desirable in some situations, such as tandems or very heavy riders.
A large amount of the strength gains in the more expensive tubesets comes from the heat treatment process. Typically this means achieving an optimum and stable distribution of carbides in the iron matrix. Subsequent operations involving brazing and TIG welding can upset that distribution of carbides, so for the high strength tubesets it's more important to have a highly skilled frame builder who is sympathetic and knowledgeable about the impact of his/her activities on the steel. For example, the Reynolds 753 grade was supposed to be assembled using silver solder rather than conventional (brass) braze metal, as it reduces the temperature required.
The 753 tubeset was the first heat-treated tubeset in the race bicycle industry, based on the same alloy as 531. Used mainly in lugged and fillet-brazed framesets, Reynolds implemented a Certification procedure for builders who wished to use the tubing, as it helped builders understand the...
www.reynoldstechnology.biz
I believe that tube butting has two different roles to play here. Firstly, thickening the ends of the tubes ensures that there is extra material in areas that are subject to the highest stresses. Secondly, thickening the ends of the tubes ensures that there is extra material in areas that may be slightly weakened during the brazing or welding process.
It is for the rider and framebuilder to decide what is the best balance of cost, frame stiffness, and lightness. And the requirements of a cycle tourist carrying a tent, sleeping bag, stove etc will likely be very different to someone doing day rides with minimal equipment. The only other consideration I can think of is that, like titanium, 953 doesn't require paint.
