I thought of this question as I was coming up with answers to the threads that these two dates were mentioned. In 1959 I think I would have made Plus-X my "all around" film as it was improved by Kodak in 1958. Tri-X at the time might not have served as well as a multipurpose film. For color slides Kodachrome and for more speed Ektachrome. By 1971 I would have probably used Tri-X more often than Plus-X. For color I would go with Kodachrome II. For more speed High Speed Ektachrome. For color prints I would use Kodacolor-X.