1 pump, 2 pump

[reef tank 2.0]

In my world of tank set up, and constantly changing my mind on how I'd like to do things for an easier set up, I've hit another fork in the road.

RODI / Salt water bins - On my last set up, I had one Eheim 1262 that I'd use to pump the salt water into the sump for water changes. The second bin which was clean RODI water was used for topping off, which I manually took 1 gallon of water from each day via the ball valve on the front. All well there.

Now that I am setting a different tank up, with a totally different layout than the last, I have options. Mainly in regards to how the water gets pumped from the water bins, over to the sump.
I have (2) Eheim 1262 pumps, currently planned on putting one in each water bin. Whether I am doing a water change, or a water top off, I'd turn the pump on and shoot the water up, over, and down into the sump. The only cost there is pvc / fittings / valves.

I see a lot of people that use one external pump, and then turn valves one way or another to close off the section if pipe they do not intend to use. I assume in that case, it's one less pump they have to buy, So it's a cost issue. From what I can see.

Anyone have any input on which set up is the better choice?

 

[KrisReef]

Two. I get confused easily and turning valves becomes a high risk adventure when I am tired.

 

[Sean Clark]

You can use a 3-way valve. One valve, one pump, clean and simple.