A few questions:
You don't mention the return journey with the Gulf Air option. Is it a long layover?
Will you need a transit visa for the overnight stopover in Bahrain?
It doesn't appear that your itinerary with Gulf Air would earn you Avios points. Is that enough to tip the balance to Finnair? I myself am an Aeroplan member, and when two airlines are relatively equal in price and journey I will go for the option that gets me Aeroplan points.