Deca for a longer bulking cycle, fina for a shorter cutting cycle. If your looking to pack on a lot of size fina is not a great choice, most of the poeple I know that use it barely gain any weight and see more of a change in BF% and strength. Almost everyone I know that has used deca has reported great gains from it even if some of that is water, your still packing on the most muscle. Besides, you can gain a lot more in a 10 week cycle than in a 6 week cycle while putting less stress on your system, so personally I would go with the deca(although fina is good, i will be using it to try and cut/harden up for a show later in the year).