I have both and love both but I do get more use out of my PS1 (mine is the small so the same size as a 227 reissue). I believe that both bags are classic (the Chanel is a proven one and the PS1 may be in time as well) but I would buy the one you know you will use.
The PS1 is lighter than the flap in the same size, but since you are considering a large PS1 vs a reissue (largest being a little larger than the small PS1) I am guessing you have a different purpose intended for each.
The flap will work as an everyday bag if you don't carry much but if you do, the PS1 just makes more sense.