When deciding which whole-house system is best, you need to know your water usage, the contaminants that you need removed, and your budget.
Whatever system you are considering, look for certified performance claims like UL (Underwriters Laboratories), NSF (National Sanitation Foundation), and/or the California Department Of Health Services for safety compliance and quality.
Ultimately, the filter you pick must have the ability to remove whatever contaminants you want to remove from your water. This EPA website will list your city water quality report for more detailed information.
I have an Aquasana whole-house system. After some research, I found that this product was most cost-effective based on the quality of the filtering ability that I wanted for my family.
Some folks love the reverse-osmosis systems and others swear by the carbon-filter systems. Reverse osmosis does remove more impurities but can waste a lot of water.
Hope this helps.
For more information:
You should also read Gary Shlifer's Ask A Pro Q&A, "I have a private well and want to add whole-house water filtration to reduce iron and hardness. What systems are most energy efficient?"