I am no drift boat expert, but from the info that I have gotten on drift boats recently says that the 16 and 17ft are both 54" wide. The 17ft is also just a 6" longer than the 16ft so your reall not gaining a whole lot of space. However there is more room behind the rower so you can store a cooler or something of that sort back there.
I would definately get the heater system for those COLD winter steelhead days.
You might want to give willie boats an email:sales@willieboats.com
They are great guys and should be able to help you out!!!

Good Luck
CatchAZZ laugh