Re: Which water filter is best?
There are newer reverse osmosis filters that waste less water. For example, the VGRO-75 wastes only 50% of water while removing most of the contaminants you mentioned including VOCs, chlorine, fluoride, chromium, lead, mercury....etc.
Combine this with a small UV filter and you will also be able to disinfect the water.
You're right about the pH. However, most of the time it's only slightly acidic. Less acidic than orange juice. Even that level of acidity can be easily neutralized by a calcite cartridge added to the last stage of the ro filter.
De-ionizers are mostly used in aquariums and semiconductor industry where water conductivity should be at a minimum. De-ionized drinking water does not taste good.