That article compared SM1.1 to 3.0, not SM2.0 to 3.0. However, that is a good comparison to make because future games will only support 1.1 and 3.0.
SM2.0 is much, much better than 1.1, but not as good as 3.0. The major thing you will be losing by not having SM3.0 support is support for HDR rendering, which will be a big deal in the upcomming "The Lost Coast" mod for HL2. You will need a SM3.0 capable card to experience HDR on that game. SM2.0 cards will be able to use a "bloom" effect.
However, since future games will not include support for SM2.0, you will be stuck between 1.1 and 3.0. And believe me, you don't want to be playing these future DX9 titles in DX8.1 compatability mode, which you will be doing if you get the X800XL.