I'm in on the '99 Speedster ( I have one). Personally I not a fan of the rear seating of the Challenger boats and personally have never driven one. But that being said consider the Speedster a 4 seater as the bow seat is the bouncy seat but it truly is a 5 seater, the Challenger may feasibly fit 5 better. The Speedster is 16.5 foot long, a full two foot longer and a nicer hull and in my opinion will give you a nicer ride in rougher water--still not as nice a ride as the larger Challenger 1800. There are tons of lakes up there so the rough water might not be a concern, so the bouncy seat might not be a deal breaker. As a personal preference, I like the twin 787's over the twin 720's but both engines are great engines for sure if properly maintained. A compression test on each engine would be great as well as a decent length test ride too, just to see if any issues rear their ugly heads. Either way you can get in deep on costs if they need repair. If you have any pics you can post that would be great, inside, outside, engine bay, etc. I know of a guy in Gander (if he still lives there) that is wicked good with Skidoos and Mustangs, not sure where you are. Best of luck in the search.