I would suggest you go online and Google and read the reviews for all of these machines. My issue with some of the reccomendations here, however, is that they are way too heavy. Weight is your biggest enemy in motorcycling--and i would assume--although i know nothing about ATV's--that it would be a similar issue for ATV's, although it depends what you are using the ATV for. Weight effects your horsepower, your fuel economy, acceleration, deceleration, braking, cornering, and a host of other meaninful things.
If you're going to be living on a farm and hauling around pigs, hay, farm supplies, and a heavy wife, then yes, go for something with extra suspension and weight. However, please realize that you're fuel economy will suffer, your handling will suffer, and the only way you can "offset" poor fuel economy & handling is by either using an ATV that weighs much less--and therefore gets better fuel economy and better handling--or getting a new wife or pig to haul around.
With motorcycles, i'm as about as close to an expert your're ever going to find within the perimeters of say...Sosua and Cabarete--but excluding west of Sea Horse Ranch. I own several motorcycles--both here and in Norway: here i own a 2006 KTM 950, 2008 Husaberg 550, 2003 Honda CBR1000RR, 2011 Yamaha fuel-injected 125 Zuma, and over in Norway a few more motorcycles.
With motorcycles, weight is your number one enemy. Period. Unless of course, you are touring around Europe or the USA with a heavy wife and you do not want to sacrifice comfort for say...better fuel economy and handling. If comfort is your number #1 issue, however, then yes, go big, go heavy, and get yourself a big woman who can give you shade in the summer and warmth in the winter...plus she will also provide more cushion for those romantic moments when you find yourself on the side of the road and there are no Artic dealerhips or Polaris parts or distributors or dealerships within 5000 square miles of the Dominican Republic.
Yes, The KTM dealership in santo domingo is a Polaris distributor, but don't think for a second that they carry any spare Polaris parts on hand. Not even remotely...unless of course you are looking for an air filter or oil filter. I'm good friends with Daniel Abrue--who is part owner and head mechanic of the KTM/Polaris dealership; i'm at the dealership a lot. you could say that i live there part time. I've bought more then my share of KTM's from them--as well as a brand new 2008 Husaberg 550 right off their showroom floor...because it looked lonely and i only owned 6 other motorcycles at the time--including a 650 Husaberg in Norway. Yes i have pictures of all my babies for anyone interested in seeing them.
Anyway, the number one question is what are your needs and how far can you see youself traveling on your ATV. If you are like me, and like to traveling around the island--both off road and on road--then you want a V-twin engine and not a single cyclinder. The V-Twin will make cruising down the highway with two Fat people (I have a fat stomach) remarkably effortless. A V-twin (two cyclinders for those not familiar) will take you to the moon and back, and you will have the comfort in knowing that if its a Honda or Yamaha then the spare parts can be bought readily and easily--right off Amazon.com in fact.
If heavy hauling, however, is your main thing, and you and your wife are living large--as in big boned people--then go for one of the other suggestions, but be aware that with weight, you will sacrifice fuel economy and accelrations and decelaration--it has to with a little known equation of Mass x intertia x a lack of a Flux Capicitor button.
Personally, i love the fact that with the "Fuel injected" Yamaha 700cc Raptor, i could pick it up--either the back or front--and move it in whatever direction i wanted. i could easily pick one end off the ground. That, coupled with the fact that the acceleration, and lack of mass, resulted in near rocket level performance...it enabled me to travel so fast that i went back to the future and came back and did not age one minute. It sold me right away. The reason is simple, but it has to do with Math: Speed x Insane acceleration x a shot of Adrenaline x Balls retreating up into my stomach, equals fun.
But, don't take my word for it, research them all and try them out if you get the chance.