I'll have to disagree (slightly), the only technical difference of any importance between Columbia and Schwinn was that Schwinn used more balls in the headset bearings than Columbia (or any other U.S. maker). - Schwinn used 17 balls per bearing, and Columbia and others used 15. Raleigh (I think) used 20 or 21.

What sets Columbia and Schwinn bearings apart from other American companies is that the bearing surfaces are curved to give a larger contact area for the balls. In other U.S. brands the cones and races are flat, and commonly you'll find that they show impact damage.

Schwinn also did a neat little trick where the top bearing in the headset was upside down - this kept water from entering the bearings.

Schwinn and Columbia also sourced a lot of parts from the same companies too - Union (German) made Pedals, Weinmann brakes, Huret derailleurs etc. (actually, Columbia originally started out using Simplex, then followed Schwinn to Huret, which I feel was a step in the wrong direction).

Objectively Columbia was only ever a notch below Schwinn. Although if you care about weight, then maybe Columbia comes out a notch ahead - in addition Schwinn stuck to forged forks, when tubular blades offered a lighter, better riding fork.

I'll have to say that even Murray and Huffy made some acceptable bikes. Disregarding their inferior bearings and other minor detail differences - I'd rather ride around on one of Murray's hydrogen brazed frames than one of Schwinn's electro-forged frames any day.