I think size or shape of the tank has a lot to do with what kind of marine life will inhabit it.
As a general rule I believe is best that a reef have fairly good width, so that proper water flow becomes more feasible. I personally dont like wetdry filter systems. You could go to your LFS and have them custom build you a sump. You might want to have a small refugium built in also.
If your budget allows you to buy a skimmer, then you could do without the refugium(for lack of space) and just place your skimmer in the sump.
Amiracle makes some nice sumps with refugiums.
http://www.amiracle.com
If you are considering a 75 or a 100, upgrade just a little more and get a 120(great size tank and optimum shape, when considering an SPS reef)
Main advantage of a custom built sump is the option of building any size to suit needs due to room availability.
Doug there are many reefers that still run a Wetdry filtration systems, but numbers decrease every day.
JMHO