I'm just guessing, but I doubt the "PUR" faucet water filter will be as effective as a RO/DI unit.
The RO/DI system eliminates 99.9% of all pollutants from the tap water. It's so clean, in fact, that it actually depletes the water of its oxygen.
PUR filters are new to me, however I'm guessing they don't filter water as well as RO/DI devices do. The PUR faucet water filter costs $25 at my local grocery shop. My RO/DI system set me back well over $1000.00. I'd like to think that I received value for my money. If you discover that the PUR filter performs the same function as my RO/DI unit, please do not inform me, as I shall weep all night.