Check the detailed specs on all the brands you're considering. If you don't want to dent the deck on the first rock, look for thicker steel. Some of the manufacturers use 3/16 steel for the decks with 1/4 inch side skirts.
Also look at the deck reinforcements, particularly where the gearbox bolts down.
All three brands make pretty nice units, but some are better designed than others, IMHO. Only you can decide what is best for the weight your 3PH can handle.
All that said, I have my eye on the "New for 2011" Land Pride units, which I think are designed quite well... on paper at least. I'll reserve official judgement until i see one in person and get to crawl under to check "the bones..."
BTW, The Woods units make blade maintenance a bit easier by doing away with the huge 1 11/16 nuts and high torque values.