200+ pounders don't need light weight wheels, not that most bents have a lot of choice in the sub 650 sizes. I agree with uprightbent, the most important thing is to get the bike and ride. Once you have a year or two experience, and perhaps some weight reduction, he can consider whether a lighter bike might be in order. Rider weight is by far the biggest factor, and after conditioning has improved the power to weight ratio.
Steve