Hi Mullermeister,
You have to make a lot of assumptions in order to answer your question easily. The first is that viscosity's effect is a constant drag coefficient (meaning that the drag force is proportional to velocity and constant over all velocities). This can be a good approximation, so long as the velocities are relatively small and the viscosity isn't too high.
Next, you have to tell us how to measure "reaching terminal velocity." You never quite reach it, though you can get as close as you want. The natural way to measure it is to say "how long will it take to reach X% of terminal velocity?"
Under those assumptions, the one with the higher drag is always going to win.
I know this because under the above assumptions this is fortunately a very simple problem to model in physics, and the result is:
v(t)=v_{terminal}[1-exp(-t b/m)],
where t is time, m is the mass of the object and b is the coefficient of drag--b is larger when the drag is higher. If you're math-savvy it's not too hard to see that from this equation, you reach any given % of terminal velocity faster when the drag is higher.