You’re looking at a 17’ boat so consider its size/weight. Add in you and 2 growing boys, a 40hp is going to be a bit slow. A 60hp will only be slightly faster though. Top speed probably about the same once shes out of the hole, but thats limited by the hull shape. Hole shot will be the biggest difference.
The boat in that ad is a 50hp. See it here
https://www.trackerboats.com/bass/bass-tracker-classic-xl.html
So its a roughly 15% power loss, but being a newer motor, probably even less. Also note that the new tracker has a max hp rating of 50hp, and dealer states 30-35 mph. My deep-V starcraft only goes 30-35mph with an old 2 stroke 75hp (60hp modern 4-stroke equivalent).
I would argue all day to go for the new boat with a new, 0 hour motor under full warranty, interior and hull in new condition, full hull warranty, and new trailer. For the few thousand more, you are getting a lot.