I am with Bruce. The newer model looks more "impressive" with its modern style, but the "classic" Genesis, I think, has a timeless charm and rugged reliability that the new ones lack. You could have some fun following some tips from this forum and do a complete renovation of your 1300 making it look better than new.
Does your 1300 have wood slats?
Also, is the S320 the one with side controls and "E-W" burners or does it have front controls and "N-S" burners?
I would definitely rather have a 1300 than a new one with front to back burners.