I was skeptical about whether the weight difference would actually matter, but moving up to the heavy double ball made a noticeable difference within a couple weeks. The step from the soft single to the double is a real jump, so give yourself time before sizing up.
Hannah★★★★★
Started with the soft single ball for a week before moving up, and the progression actually makes sense instead of feeling like guesswork. By the time I got to the heavy double ball I could hold it through a whole workout video, which I definitely couldn't do at first.
Christopher★★★★★
Didn't expect to actually feel a difference, but after a few weeks the single soft ball goes in easy and I can hold it through a whole dog walk. The jump to the double ball is real though, so don't rush it.