I'm looking for an all-around tire size. Is there a significant and noticeable difference between 28 and 32 size tires for my 700 wheel? I won't be touring much this summer but I'll be riding plenty around Vancouver, mainly commuting and shopping etc. My rims are Mavic 520s and I weigh about 200 lbs.

If your not touring I don't see any reason to go with 32's unless you have rough roads or gravel you'll be riding on then the 32's will give a bit more cushy ride, plus with 200 pounds of weight on the bike the 32's will reduce pinch flats caused by the rough roads.

A lot depends on tire brand. For instance, Continental Top Touring 700x32 are 29 mm wide on my rims, whereas the 700x37 are 36 mm wide. And IRC Tandem 700x30 are 30 mm wide.

So:
- will you be riding for utility?
- how are your streets, bridges...?
- how much you weight?
- do you value speed or comfort?

An indication might be the pressure you like. If you can't stand tires at more than 90 psi, then go for 32 mm; but if you like 125 psi tires, go for 28 mm.

My experience is that as tire size goes up, you can handle more difficult terrain. For me, I'd use 32mm only if I were going to be riding significant gravel or if I were unable to avoid potholes. I find 28mm to be good for most urban conditions.

Generally, thinner feels faster and more fun to ride.

It also depend on you/your load's weight and your riding skill. Heavier rides usually use wider tires. More skillfull riders can manage bad road conditions even on thinner tires. Use your own judgement here.

as mgagnonlv said above, the actual width of the tire is what matters and the label may or may not match the actual width. Within a brand, the label is good for comparison though.

I notice a difference when I switch between the two sizes. I keep 28 for summer and 32 for winter and loaded touring.