dirtworksequip pretty much said it all and Squizzy has valid points too.
You have to keep in mind that when a track loader has a full bucket, most of the weight is then transferred to the very front of the machine, and that is exactly the part that is usually trying to turn. You may notice that a loaded machine turns very easily when backing up as compared to moving forward. So you want to position yourself so that if you are loading trucks, you turn coming out of the bank backwards, and then go straight forward to the truck.
Single grouser loaders are very rare and are usually used in a specific application where traction is the largest single factor. Squizzy's loose sand or wet muck and clay come to mind. I think I've only seen one of the newer Cat track loaders with single grouser type shoes, and it was being used in a swamp. This type of shoe does tend to tear up your work area too, so the street shoes are better in this regard. Single grouser equipped machines also take more power to turn and so fuel economy goes down.
Generally speaking, the street shoes will last longer, unless for traction under-foot reasons the machine spins the tracks a lot. Spinning tracks equals faster wear, and loss of efficiency of course.
You can get your machine equipped with anything you want, it just depends on your most prevalent type of work as to what you choose.
