I think most pro racers praise a stiffer frame for when they are out of the saddle sprinting. The length of the seat tube may be moot under those circumstances.
I bring up the racers because the OP asked about performance features of the compact vs the traditional. I suppose you could list comfort and ride quality as a performance feature but that was not the way I took the question.
Quote from Giant's literature (Giant is recognized as the modern era developer of the compact road frame) " Giant’s Compact Road design is arguably one of the most important developments to hit the peloton since Lycra. So significant is the design that the Union Cyclist International (UCI) was forced to change their rules regarding frame configuration. And bike makers, from the most respected European custom builders to the largest companies in the world, have adopted the design.
By sloping the top tube downward toward the rear of the bike, two very important characteristics were achieved. First, the frame became stiffer for improved acceleration and more solid cornering. Second, the bike got lighter."
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