27X 1 1/4" was pretty much standard on most bike boom era offerings. It's a touring tire size. As you went upscale performance wise, 1 1/8 and 1" skinwalls were offered.

I personally didn't notice a difference between the sizes, with both wheelsets built for performance. The 27" were Campy Record hubs, DT spokes, Ambrosio Elite Durex with Specialized Ultralights and Turbo /S. 700C also Record hubbed, DT spoked, Campy Omega Strada clinchers, and Panaracer wire bead Technovas. 27x1" vs. 700Cx25mm.

Ride characteristics very similar regards to acceleration, harshness over bumpy surfaces, cornering, braking. One didn't roll any worse or better.