I think it depends on your goals as a pilot.

In my opinion, a second plane should be used to improve your abilities and increase confidence. It should be easy to handle on the ground, do basic aerobatics, have a decent vertical capability, fly honestly, be durable, cheap, easy to repair, simple to set-up, and above all else, not be scary to fly.

I always recommend a stick as a second plane. There is no other plane that will let your skills and confidence advance faster than a stick. The simple reason is that you'll get more stick time and when you fly, you won't be afraid to push your limits. Not only that, it will cost you very little money and will build quickly.

Save the cub for another day.