YankeeJim, in my opinion they seem to be marketing to different crowds. Yes there is some crossover...folks like me just like a good golf sim to play. TWO is funded by EA Sports, and they cater to the console game crowd in all of their sports games. If you look at the advertisements here at WGT, you'll see they are all upscale, high end products...not exactly what a 20 yr old console gamer would be able to afford.
So, both have the ability to maintain longevity: TWO through being able to reach far more people (and younger people), and WGT because it caters to players who have a higher annual income to be able to afford the upgrades.