Hondaguy,
The Amsoil 10w-40 is the better oil, but I'd recommend you buy it locally rather than from me. I've been working to get more retail outlets to carry Amsoil and I like to refer local customers to one of these places. People just seem to think a product has a lot more credibility if it's sold in a retail outlet, even if the folks actually selling it know very little about synthetic lubes.
Just to confuse things, you could also run the Amsoil 0w-40, "four stroke" synthetic, which has been formulated specifically for these applications. I think the new Polaris engines call for a 0w-40 for example.
TooSlick