We drink a LOT of water at my house, and we like it COLD. So after we accidentally ruined our Brita pitcher (whoops, not dishwasher safe) we got a replacement. The Pur was slightly cheaper, so we bought it. My husband was interested in the "Flavor" option that came on the Pur filter. It allows you to flavor your water with the push of a button. It adds a few drops of flavoring as you pour the water. While a cute novelty, we never use it. We have both tried it once, and never since.
My favorite feature is the filter replacement indicator. There is a small LED light on the top of the unit that you reset each time you change the filter and it blinks green, then yellow, then red as the life of the filter expires. I am horrible at remembering when i changed them, so having something to keep track for me is AWESOME, especially since it doesn't involve stickers, making notes, etc.
We chose the pitcher over the tap filter because we do like our water cold (so we refridgerate the pitcher) and the replacement filters are much cheaper on the pitcher.