The marine exhaust hose is construted of Viton rubber, it's made for that purpose and will last quite a long time! Silicon hose is simply gas resistant, it will last for awhile but the gas and oil in the exhaust will eventually take it's toll.
For the money though, silicone is about the same price but just a little cheaper. If you decide to use silicone I would recomend using
http://www.hightempsilicone.com/c=audiM4OIAHkQXO1LeRnpmWtDL/ ====HIGHTEMPSILICONE====
They've been good to me and have any size you want for a good price!