We sailed DAWN Princess before.A lovely ship. The balconies '' holes'' are really big size. A full balcony recessed instead of jutting out.,and there is even a railing inside the steeel wall. The '' cut out''are full size; your view will not be hardly diminished.
This ship handles crowds very very well; perfect size, imo, at approx 2000 pax per sailing. Compares with your other choice, MERCURY, as far as size and crowd flow is concerned. Both the same age.
Celebrity is a cut above Princess over all, but we're not talking HUGE differences.
More balconies on DAWN than MERCURY.
Dawn also sails ( this year anyways) ex SanFransisco, Mercury from SanDiego.