I have both the 17 and an Officers Model Match .22, basically the same as a 1st Gen Trooper (not the Mk3, that is a totally different gun).
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Both are 6" and equipped with the optional Target grips and hammers. The 17 has an optional Target trigger, but Colt didnt offer one. Both have fully adjustable micro-click sights, with excellent sight pictures. There are 17s and Troopers out there with smaller "Service" or "Magna" grips, and standard, thin hammers and triggers. Something to pay attention to, if it matters to you.
The Colt has a slightly lighter, smoother DA pull, both have excellent SA triggers. The Colt is heavier, as it is built on the beefier Colt "I" frame- same as the Python. The 17 is built on the S&W medium K-frame. Both are plenty strong for the task.
In my hands, the Smith edges out the Colt in the accuracy department, but only just- both are VERY accurate target revolvers. You may notice the extra bulk of the Colt after a few strings of slow fire.
Assuming both are in perfect condition, the Colt will probably command a somewhat higher price. Both are great guns, but if I could only have one it would be the M17.
That said, if a clean Trooper comes your way for a reasonable sum, snag it. You wont be disappointed either way.