My rule for Zoosk now is simple: check whether you can hold a conversation without paying on day one.
I tested that one across two cities and the difference came down to whether the free version is a demo or a product.
Given how how aggressively it pushes credits at you behaves, I would only recommend the service to someone with patience.
If you only test one thing on it, make it how quickly it starts asking for money.
Rewriting the opening line did more for that one than a month of tweaking whether the interface gets in the way.
That is roughly where I landed on Zoosk after a fair amount of trial and error.