Submersible pumps and splitting return line

[Reflective]

So as I'm planning out all my new plumbing I decided I really don't want to drill holes in my new sump. So I am going to replace my external pumps with a submersible one.
I currently have two Pan World 50PX-X hooked up to two 1" returns and I redirect a lot of the water back into the sump because they seem to put out way too much flow.
I was thinking about buying only one pump as my return pump but wasn't sure on the flow if I split it. I'm trying to get about 800-1000 gph going through the sump loop. Does it matter if I split it? Will the flow still be the same? Also should I try to go for a bigger outlet on the pump and reduce it to the 1" after the split or will a 1" outlet be okay?
Or I could by 2 smaller pumps, but the outlets are usually 3/4". How much does it affect the GPH when you go from a smaller outlet to a bigger pipe?

 

[ATB USA]

By splitting it you loose pressure, not output. Saying that, you do loose a little output due to the increases head pressure. (The fact you are pumping water up)
3/4" over 1" would give you higher pressure coming out. Look at the force of the water in your sink vs the bath tub.
If you use two smaller pumps. they take up more space.
If you use two smaller pumps and one fails, then you still have flow.
Depending on head pressure, two smaller pumps may give you more pressure.
If you do not have a lot of head pressure, A larger pump may be better.

 

[steve&mari]

Also remember 2 pumps is double the heat added to system. I run 1 dc pump for return and split it off feeding 3 reactors without issues. Pump puts out 1320 gph but being a dc pump with a controller I run it at half power to have the flow I want but can ramp up to stir up stuff in rocks for water change.

 

[Reflective]

I was going to split it for the two returns and also split it for 2 reactors. It's only going up 5 feet from the sump to the top of the tank. What kind of DC pump do you use? I was looking at the Waveline ones