We have a thread
going on the 2730....do you know any more details than what we have listed in it?
As far as the 7200 & 7500, neither of them appear to be waterproof. They are being marketed for RVs and semis. They are probably too large for motorcycles anyway!
NONE of the 3 appear to be capable of NEXRAD radar - at least for now. According to one post, they have a package deal from XM that includes XM Radio, XM Traffic and XM Weather (dumbed down version) for $17/month here in the US. The weather appears to simply be a forcast like you get on the Weather Channel.
That package for the 376c is $30 - $35/month (depending on what post you read), but includes NEXRAD radar. Maybe the 2730 simply needs a firmware update and a better subscription? I have emailed Garmin and asked if they will offer a version for the 2730 that includes radar.