I noticed you have not gotten any replies on the Ocean Breeze so I thought I would chime in.
I have NOT used Ocean Breeze, so I cannot give you a specific rec there. However, I have used Cruisair on my last three boats and have been very pleased. Never had a problem heating or cooling with them. Period.
I would like to give you some thoughts:
1) 18500 is a big unit. You might be better served with a 16k or two 12s. My reasoning: The power you get on the docks is usually horrid. You might find yourself tripping the breaker in some marinas. We tripped them in the heat of the summer when our 16 and 8 (I think it was an 8) kicked on about the same time. Our way around it was to boot up the 16 first, then the other (sorry, I cannot remember if it was an 8 or not now). But, you get the picture.
2) The tendancy is to wire in to the existing dock power coming into the boat, and that may be a mistake for the reasons listed above. Put the A/C on its own shore in. Most marinas have two 110s out for that purpose. Worst case scenario, we would carry a pig tail with us. It costs a little more, but you will come to thank me.
3) Plumbing. When you plumb for the water, do NOT use the pice of crap strainer that comes with it. GO buy a large bronze strainer (the bigger the better, to a point). THe small strainers trash up so quickly (especially in the warmer waters) you won't believe it. You will be down there cleaning the strainer three - four times a week if you don't use a large strainer.
4) T-Fitting. Obviously you will put in a strainer on the outside, but we also plumbed a "t" above the T-Hull with an on/off valve above it. That way when you sick up a palm leaf or plastic bag (which you will do) you don't have to dive the T-Hull. Just open the valve above and plunge a coat hanger through it which will clear the strainer. This is also very useful for hooking up a water hose to flush the unit with clean water and priming.
5) T-Hull location. THis is very important: DO NOT put your t-hull in the stern. Put it in the lowest part of the boat. AC's lose their prime very easy and every time a sports fisher goes by you will lose your air conditioner if you do not put the suction low. This will also minimize the junk you pick up in the tropics and elsewhere.
6) Accesibility. THe T-Hull should be very accesible for clean out, or you will come to hate your air conditioner.
Hope this helps. Best of luck to you. Sorry I could not give you a rec on the Ocean Breeze, but maybe a little helpful information otherwise. Cruisair is a good product.