STA difference is irrelevant, as your saddle position relative to the BB should be static regardless of the frame size. So that means the reach to the top of the headset would be 15mm longer on the larger frame? Then your stem will be 15mm shorter for the same bar reach, reducing "tiller" and will make steering feel quicker in low-speed situations. The longer FC will tend to make the bike feel more stable at speed, though. Noticeable? Depends on whether you're the princess that feels the pea under 20 mattresses.