Woah, 15lbs? The Franchi Instinct SL in 12ga is 5.7lbs in 28" and 5.6lbs in 26". Its the aluminum frames on these guns which makes it so light.
Sheridan is basically correct although I see a lot of upland hunters using autos.
The choice is really yours. If you value craftsmanship, then a double barrel may suit you. There not many double barrels gun with polymer stocks. If you are more into utilitarian then the auto may suit you. Both are fine. You have to weigh your budget and usage.