Sump vs refugium

This one comes with a skimmer and the one I have isn't so good, so it will probably replace the one I'm using.

 

What do you mean by "this one comes with a skimmer"?
Does the refugium come with a skimmer?

You're not putting the skimmer into the fuge, or feeding the skimmer inlet from the fuge are you? That would be a BAD idea, and defeat the real purpose of the fuge.

Are you planning on putting the skimmer in-line between the tank and refugium? If so, I don't think the right amount of (slow) flow through the fuge would be able to support the (fast) flow for the skimmer. If the flow is slow, as it should be, the skimmer will be sucking air cause the flow won't be enough to supply it.

If the skimmer is going to be in a separate chamber adjacent to the fuge area and in-line between the fuge and tank return, then it would need a faster water supply directly (maybe T-ed off from the overflow) from the tank to that chamber, and that area would essentially be your 'sump'.

The only setup I'd use a fuge over a sump w/ skimmer would be a coral/reef only tank with no fish, or maybe one little fish that produces little to no bioload. If you have fish, you have bioload and need that skimmer in a sump more than you need a fuge.

Bottom line, I don't think a fuge can take out as much waste from a tank as a (working/efficient) skimmer in a sump could.

 

I misunderstood. The sump comes with a skimmer. I'll most likely run the fuge first, and then sometime later add a sump (with the skimmer built in).

 

I would never add a sump to any system for the purpose of increasing the total gallons of the systems water . A sump if running properly will not add much water at all like on a say 90 gal. tank with a ohhhh say a 10 gal sump and the 10 gal sump running at 4 inches of water depth you have not added more then 2 gallons of so . A refugium will add more water volume but its not a sump they are both equally important and much needed .
But like already mentioned a sump should have its water mixing as as turbulent as possible for the skimmer it do a better job.