Also comes down to how much space you want to give up for it.
1/350 is cool, but something like a Nimitz, or Enterprise (modern) carrier is huge at 1/350. The flip side is that if you thought the aircraft was small at 1/350, they are half the size at 1/700.
Lord knows I have enough ships in my stash to out boat the Canadian Navy, don't build nearly enough of them. Most are 1/700, but a few key 1/350 in there.
Then of course you can go whole hog, and get into the 1/200 ships, Arizona, Bismarck, Hornet, Missouri, with the Hood due out later this year.