I made a similar change with a Campag Chorus 53/39 crankset, swapping the 53 for a TA 50 from Peter White. The reason for reducing the chainring was that it put me down into the middle of the “corncob” region of the cassette for normal riding. With the 53 I hardly ever used the smallest couple of sprockets — the 50 essentially shifted everything down one sprocket. It was a good move for me and there was no deterioration in shifting. I lost a little top end, but I didn’t miss it. TA rings are excellent quality.