Powerhead/ Waterflow question

I was looking into the Tunze powerheads (the nanostream ones), and I havea 75 gallon tank. so my question is would it be better if I got 2 of them that each have 660 gph or just 1 that has 1189 gph. I'm not sure if having both would be better or if it would be ok with just the one. thanks
 
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