It depends on the amount of motivated employees.
If you have more than 5 employees willing to commit to their challenge - then it surely makes sense to subscribe. If you will have difficulties finding 3 employees to open a challenge, you will be better of by sponsoring your employees without setting up a company in the system.
It will be cheaper by supporting the individual challenges (when sponsoring them, use the companyname as alias). But the disadvantage will be that your company will not appear in any of the overviews.