The different TA recommendations have to do with what you are using as the primary source of chlorine. If you are using trichlor or dichlor, they are both fairly acidic and you need a relatively high TA level to keep that from getting out of hand too quickly. In this situation TA should be at least 100, and probably higher.
If you are using bleach, a SWG, or cal-hypo, all are long term PH neutral, so you have more flexibility about where the TA level goes. If there isn't too much aeration, which I will get to in a moment, we recommend keeping TA between 70 and 90 in this situation.
One additional concern enters in when using a PH neutral chlorine source and there are significant amounts of aeration. A SWG always aerates and fountains, waterfalls, etc can also provide aeration. TA does two different things, it helps slow the rate of PH change, and it puts upward pressure on the PH (because of dissolved CO2 over saturation). When there is a source of aeration, the aeration allows the excess CO2 to outgass, and the rate of PH increase goes up. In many situations, CO2 outgassing encouraged by high TA and aeration becomes a significant factor. Targeting even lower TA levels, between 60 and 80, helps minimize this PH drift.