I think extract/tincture would be easier to control the final flavor, yes. I would advise making your own extract, however, as many commercial ones add "unnecessary" ingredients IMO (like corn syrup and salt). It is very easy to make. Just get some fresh vanilla beans, split them in half lengthwise, and add them to 100 proof alcohol (rum, vodka, 50% everclear and 50% water, or whatever). Let is soak in there for a month or so. If it is not dark enough, add more beans.
When i am working with a specific ingredient i usually brew 5 gallons minus the ingredient. Then i take 1 gallon and place it in a glass jug for the secondary and add the special ingredient to that. This way you have four more gallons to experiment with. Remember, as Emril says: "You can add but you can't take away."