Personally I like around the 300-400 range in others art. Big and soft is nice and many people are very good at drawing those sizes. It gets more iffy as you go up in weight, but 300-400 seems like a good size which balances heaft and reference availability.
I enjoy drawing starter bellies more than anything else personally.
I'm just still more accustomed to the anatomy of thinner people and starter bellies retain a lot of that basic form without compromising the human silhouette. They're also very cute to draw because it's more subtle at that stage. Conceptually they're one of the best sizes to me too.