Peter...I have used, and still use, both ASM and MRC products. I have always liked the ASM, but a '3' would not be the right size for a 200+ gallon system IMHO. You would minimally need a 4 or 4x. I would use an MRC2R. It is a recirculating skimmer so it requires two pumps. If you are comparinging NON
recirculating MRC skimmers to ASM you will not be disappointed with either.
But if it is ASM..go with a '4'.