Perry:
That's a real tough question for anyone to give you a precise and objective answer to, because it's kind of like asking "What's better, an orange or a sunny day?"
The obvious differences between the two units are that the SP III is bigger and has a larger screen. But - the Quest is newer and probably works faster. Also, if you are buying a SP III, it will be a used or refurb unit, whereas if you are buying a Quest, you have the possibility of buying a new unit.
There's just too many variables there for anyone to give you a definitive answer. As others have suggested, browse through the forum here to learn more about the strengths and weaknesses of each. Personally, I would lean towards the Quest, simply because it is newer and faster, but I can't say that is necessarily the best decision for your needs. Let's just say that if after evaluating both units carefully, you still can't make up you mind, you will probably be better off getting the newer unit.
The comments made about vision (above) are well worth considering. If you have good vision and you are under 40, it's probably not an issue. If you are 45 or older, you might find the small screen size of the Quest to be a problem. Although my vision is 20/20 corrected, I would not want to use a small screen GPSR such as a Quest on a regular basis. FYI I'm 51.
Michael
PS: For the information of those posting here who are obviously well under 40 (Hi there Mutley you spazz...
) the vision problem that everyone encounters past about 42 to 45 years of age is that the muscles in the eyeball lose their elasticity, and it becomes progressivly more difficult to rapidly change focus from looking at the GPSR (typically 60 cm away from you) to looking at the roadway (focusing at infinity). This is why the small screen GPSRs are not the preferred choice of older riders. Our revenge, though, is that we can usually afford to buy the nice fancy large screen ones...
