Polar Ft4 or Ft7?

Ralstonk2

Okay. So I know a few people have posted about this. But which is better the polar Ft4 or ft7? I will be using it mostly by myself at home or at the park, but since it's getting to the spring/summer weather I will be starting to play tennis and working out with others, so which one should I get? Thoughts/recommendations? Thanks!