Welcome back Guest!MARSH is a private reefing group. Comments and suggestions are encouraged, but please keep them positive and constructive. Negative threads, posts, or attacks will be removed from view and reviewed by the staff. Continually disruptive, argumentative, or flagrant rule breakers may be suspended or banned.
I went back and forth on this a lot as well since I wanted a big pump and external is usually best for pumps in the 4000gph+ range. I typically like internal just because it's a little quieter and a few less places to leak outside the sump (bulkhead and connection to and from pump).
I ended up with the laguna maxflow internal at 4200 gph http://www.amazon.com/Laguna-Max-Fl...F8&qid=1383175826&sr=8-2&keywords=laguna+pump
I highly recommend this pump, in a lower speed. It is reasonably priced, crazy flow that I had to dial down, it was literally shooting through the overflow teeth in streams it was going so strong. I am turning it on full blast for a few hours once a week to stir everthing way up. It is the same pump that ATB sells and rebrands as their own for 3 times the price. There is a thread on RC, these are commonly used in saltwater and it is so quiet I don't even know it is on. The led fans are louder than this pump!
If you ever want to check it out let me know, I don't think I am that far from you. Also you can check out JasonC's build thread he has the 1500 version (ATB name) and has always liked it http://www.marsh-reef.org/threads/32191-Jasons-180-build . Once you see how quiet the 4200 is, you will like the 2000 range ones. This is much quieter than my Mag 24 in the other tank at less power 165w I think.
If you go external then got to check out the reeflo brand, pretty much the standard for external returns.