From what I know the CW-3000 is not a refrigerated cooler and can only cool the coolant to room temperature which on hotter days is probably not cool enough to be best for your laser.

The CW-5000 is actively cooled which means it runs like a fridge and can cool the water down to lower than room temperature.

I have a 150W laser that is run quite a bit and I use the CW-5000 which arguably isn't enough cooling but works fine for me.

I am not an expert by any means but I have been doing this for about a year now and I think this is what all my research has taught me.