Zeplin 1.0

Collaboration & handoff for UI designers/frontend developers

If collaborating and gathering feedback for your existing designs is the use case here, then I would highly recommend using Zeplin instead of Invision, because Zeplin has been built exactly for this particular use case. Just upload your existing designs and share with your team to gather their feedback. Invision, on the other hand, has several other features and they charge you for those extra features as well. Why pay for the rest when you only need one of those features. So, for your use-case, I recommend Zeplin. Cheers :)