I never cared much for whirlpool water treatment products, but that backwashing carbon filter is not too bad a selection for what it does. Unfortunately, I have seen them on well water, which I would not recommend. However, on city water, it's not too bad. Flow will slightly affected but not enough to worry about.
The other choice--BigBlue 20" filter will also serve you well and is only slightly less expensive that the Whirlpool unit, which will last longer in total volume of water it will treat. The biggest problem with the Whirlpool, is that is is very difficult to rebed (as carbon will need replacing) and nearly as costly as replacing the whole thing. With the filter cartridge type, replacement is simple and quick. Of the two, I would go with the BigBlue filter.
Get a simple chlorine test kit to monitor filter life.