I have a Viper. Hunted with it and shot it for a year. I like it.
I have not shot a Montana, but have handled one and the grip was very blocky. I have heard they shoot well. With the exception of the blocky grip, the Montana had better fit and finish (but it should be as it cost $80 more).
I did replace the Viper string with a fast-flight, on the recommendation of some folks on this and other sites.
My draw is 27" so I can't give my opinion about a longer draw on the Viper.
I did find the folks on this site were more interested in giving me good advice, pros and cons, rather than slamming the Viper as a "cheap foreign bow".
If at all possible, try to shoot both and then decide. If you ever get up to Eugene, I let you try mine!
RonP