Magnums share same cork size with 750 so Magnums are going to age much slower because of the ratio cork volume/surface to wine volume. If one wants to keep a bottle really long, magnums are ideal.
3L and above have larger corks, so there are 2 conflicted factors:
- larger cork → accelerated development
- more wine → slower development
Edward, when you mention initial accelerated maturation, do you compare it to magnums or regular 750s ? Does it mature faster than 750s?