Sump or refugium

Pros/cons of what? The kit, or a sump?

Don't know about the kit.

For a sump/fuge: more volume = greater stability
Place to hide equipment
Additional breeding ground for pods/detrivores
Allows topoff to mix before entering the main tank

There aren't many cons...I can't think of one, really.

I'm going to assume you mean a sump/fuge combo, meaning you will have 1 tank that holds equipment (skimmer, heaters, filter sock(s)) in 1 compartment , macro alage in another, and a third that holds the return pump. If that is the case, I wouldn't incorporate a fuge unless you have a specific need for macro such as a place to breed pods for food or you just want to grow various types of macro. In order for a fuge to be an effective means of nutrient control, its needs to be big. By big, I mean about equal to or larger than the display tank itslef. You would be much better off leaving the fuge out and investing in a quality submersible protein skimmer. The same holds true for the CPR fuge. It will offer little to no nutrient control benefits and you'll have a big ugly pump on your back glass .

The GH overflows do work. Lots of people use them. Are you going to drain the tank and drill it or are you going to risk drilling the tank with water in it? And before you say anything about the latter, yes it has been done. I DO NOT recommend it but it has been done. The GH kits are made well and there is no silicine involved so you could potentially drain the tank, drill it and have your tank up and running again the same day. If you are not willing to use a HOB overflow or are unwilling to rehome your livestock in order to silicone in a different style overflow, then the GH overflow is the way to go.

I agree there are no cons assocaited with incorporating a sump. Well, I guess spending more money is a con but we won't count that one .

I'm not saying not to include macro. What I am saying is that many people expect a refugium to handle nutrients in their systems because that is what they read. Of course macro will take up nutrients regardless of the size of the refugium but it has it limits. If the macro is all that will be used for filtration, the size of the fuge becomes more and more important. Just like anything else, the livestock (type and number) you keep will dictate a lot of what needs to be done in terms of filtration but I would not feel comfortable stating that a moderately stocked 75 gallon could be maintained by the amount of macro you could put in part of a 29 sump (keep in mind that you would need at least one [two if you run an in-sump skimmer] baffled off section off an area for your return pump. IMO, its not worth the little benefit you would gain over just committing to a quality skimmer and running carbon (probably should regardless if you use a fuge) and GFO.

If you like the idea of having macro in your sump, go for it. Macro does have other benefits such as a place to grow pods and keep other critters you might not want in your display.

Yes, most will, some will get shredded. The ideal "pod fuge" is placed above the tank and gravity feeds back down to the display. That is what the hang on back, CPR style refugiums are good for.

I vote no fuge and all reactors. Also you can grow pods on just LR if you want. I think some macro's are show quality (may be why I am setting up a macro tank)