I have had three of the quiet lines, a 1450, and two 1650's.
And also an 1811 and a 782 (similar tractors).
The choice was on which ones to keep, and I choose to keep the 1811 and sold the quietlines. I felt the 1811 is the best of the lot. Smooth running. Lots of little things sorted out (oil filter, fill plug for hydro, oil light, disc brakes (for a plan to add steering brakes), metal sheet panels).
Having said that, some people prefer the older tractors. And the fact that they were made by IH. The twins on the 1811 are more expensive to rebuild if needed. Am sure there are other views/opinions, no absolute answer either way, just depends on what you like.
(of course this forum is going to suggest you need both....
)