I owned bge for many years and like you with the large it had more then enough space for everything you threw at it. so the large is 18 in main grate . the 23 is 22.5 from side to side for the main grate there are 3 tiers to the 23, 4 if you count going on the basket so you could cook a steak close to the flames.
now the bge you are really relegated to the main grate unless you have an extension to put on top the main grate.
I own a 23 and let me tell you there is a lot of space and i cook for a family of 4 most of the time and have cooked for a parties of 25 and over there are only a handful of times i wished i had the 32 .the 23 will handle whatever you throw at it.
if i had to do it all over again i just might have went with the 32 but the 23 fits all my needs....
you will be very happy with the 32 or any kk for that matter
wait till you cook on the kk you think the bge produces great food the kk is in a league of its own, the bge is going to get lonely from not being used once the kk arrives lol