It might be the lower volume that you like. I'd guess you shortboard is something like 31/32L compared to 37.5L for the fish. Quite a step down. I had a similiar experience and then ended up going back up the volume a bit (handt sold my first boards thankfully) in an effort to keep my wave count super high while trying to iron out some bad pop-up habits I'd developed.
I guarantee there will be days where you need a groveller, maybe a smaller volume than 37.5l but id say if you dont have to sell it just yet, dont. You are a bit lighter than me, I'd say your intermediate volume should be around 30-32l, lower once you progress but do it too soon and you will hold your progression back, I've definately been victim of that myself.