It seems that some of the people responding to this thread are not very familiar with the
zumo 220 as many of the comments are off the mark. They may be confusing it with the
nuvi 500, which is also a waterproof, smaller format GPS. The nuvi 500 looks a lot like the zumo 220, except that it does not come with any motorcycle mounting system and also does not have the bluetooth headset output. The list price is also $100 cheaper for the nuvi.
In keeping with the comparison the OP made in post one, it would make sense to consider all of the options available:
Here's the
features comparison of the entire Zumo iineup (doesn't include the nuvi 500). These zumos are
all designed and intended to be used on motorcycles, and they are
all IPx4 waterproof and
all come with a motorcycle mounting system and can be wired to the bike. From there the features, and prices, vary.
The streetpilot 2820 is functionally equivalent to a zumo 550, but with prior generation hardware and technology. I owned one of these before I bought my 550. The biggest issue with a 2820, besides actually finding one, is that the unit has no means to expand the memory, which means that you can't load much in the way of maps, routes or music. Having an SD expansion slot in the zumos means that you can expand the total memory and load as much of that stuff as you want. The streetpilot also has no battery, which makes it a PITA out on the road. It has also been "discontinued" by Garmin so no guarantee of future map updates.
The nuvi 765T is a nice GPS, but it has also been obsoleted by Garmin. I have one, and do use it in my cars. It is the equivalent of the zumo 660 except that it has an even dimmer display screen than the 660, which is dimmer than a zumo 550, which is only barely adequate IMO. The nuvi screen gets washed out by sunlight very easily. It is not waterproof, does not come with a motorcycle mounting system, isn't glove friendly, and does not have a
useable bluetooth output (it's there, but because you can't change the pairing key code it can't actually be used with many (most) headsets). It can be hardwired to an intercom just fine though.
To be honest, if I were trying to spend less on a motorcycle GPS I think the zumo 220 is a much better option than messing around with the nuvi 765T and baggies, or the nuvi 500 which doesn't allow any means to get sound to the helmet at all.
Just to keep you all on your toes, there are substantiated rumors on the ZumoForums that Garmin will be releasing a newer zumo model late this summer. Where it would fit in their lineup is anyone's guess. I wish they would just work a bit harder on fixing some of the software "bugs" and improve some features in the zumo 66X units first before moving on to a new one.