For Me, I don't need things to look like a lawn. While the FM 2017 does a fantastic job on grass up to 8-9 inches, but when that high it leaves a lot of med-large clumps even if grass is dry. I even have Gator blades on it. Now I know I should always get it cut when it's no more than 6 inches, but even if I do it leaves clumps.
The TS is designed to cut taller grass, and still have a great quality of cut. For me, it would allow for less time spent cutting, or more importantly, allow more time between cuts, thus matching up with my free time better.
Because it has rained so much the last 3 yrs the grass grows quicker than I can get it cut, and the clumps don't dissipate quick enough before it needs to be cut again, which makes even more clumps. It takes a lot of HP to cut taller grass at 17' width, but the 4720 handles it, but she knows it there. When dry it's great.
I do like my FM2017, It is just an, "if I could do it over" thing. The TS is more forgiving so to say, if the grass got away on you, and still have a good looking quality cut. Depends on what you want, and time available to cut it.
If you want lawn/golf course look go batwing finish mower. If Country lawn (4-6") is your thing go for the TS.