stay away from all three of them. Ozone is of dubious value at best in an outdoor pool. Metals (copper and silver) are of no value at all!
Both the Delozone and Duoclear don't generate that much chlorine since they are relying on either the ozone or the copper and silver to help sanitize the water. This is not the case in real world situations. Ozone actually increases chlorine demand and metals do NOT allow you to run at .5 ppm FC as advertised if you want sanitized water!
The Chlorease is similar to such units as the Pool Pilot Cubby with the free floating cell (no longer manufactered, if I am not mistaken) which do not have an inline cell but are just placed in the pool. How well the chlorine is distributed would depend on how well the water circulates in the pool. It's main advantage is low cost.
IMHO, you would do well to stick with an inline cell SWG from a major manufacturer. IMHO, Pool Pilot digital is the best unit on the market with excellent units without some of the bells and whistles available from Goldline Controls (Hayward), Resiliance, Pentair and Zodiac (as long as you stay away from the Duoclear!), among others.