The pro have a bit better temperature dispersion, less side glare which is good ,are a little bit stronger because of the lenses, spectrum is quasi identically (maybe the old one is better as with the diffuser there is more reflection from the sand and glass like T5 so coral get light from more angles?). So a little bit better but way more expensive, this small difference is not worth the much higher price! And the price will not drop, but increase. I spoke very recently with someone from ATI, they even think to make them more expensive.. They are also no plans for now to sell them via distributors .
The only good news is here now you can get the first model for very cheap, just bought 4 news for a very good price.I will see if they are as good people says. But no way I go to spend so much money for the new model, as long people jump on the new model and are even ready to pay more than the actual price, the prices will not drop.