It depends on what you will be putting in the tank. If it is going to be lightly planted and heavily populated, you will need more filtration. Heavy planting and a light bioload will require less.
On my Over populated African cichlid tank, I have about 10 times the amount of filtration one would need on a regular tank of it's size.
On my planted tank, I am under filtering it both because I do not need more and because I do not want to loose any more Co2 than I have to. Since you are not adding any Co2, it is not really a concern.
I personally would go with the two smaller filters. That way, if one of them dies, you still have at least something to keep you going.
On my Over populated African cichlid tank, I have about 10 times the amount of filtration one would need on a regular tank of it's size.
On my planted tank, I am under filtering it both because I do not need more and because I do not want to loose any more Co2 than I have to. Since you are not adding any Co2, it is not really a concern.
I personally would go with the two smaller filters. That way, if one of them dies, you still have at least something to keep you going.