Amsterdam, move over, it seems St. Petersburg is also claiming the title of "Venice of the North". Being farther north, they just may have more credibility, or better global positioning for the title.
Of all the canals, my favorite was the small offshoot of the Moyka that ran alongside the Church of the Spilled Blood. It's narrower width was more reminiscent of Venice. In general, the canals of St. Petersburg were wider than the Grand Canal itself and bore little resemblance to Venice by virtue of their scale.
The most prominent difference between St. Petersburg and Venice has to be the parks along the canal banks. They create bucolic imagery that would be nearly impossible to find in Venice on all but the island of Torcello.