I haven't tested this but I think search engines should automatically be able to index SVGs, thus making the public maps Googlable.
In general I like SVG because it doesn't try to hide the data it's displaying, unlike flash/canvas. Although I now remember seeing a hybrid div/canvas implementation which buys you best of both worlds albeit at some added complexity.
we opted for canvas as it gives us better visualisation capabilities in the future. we could easily provide searching with canvas by overriding ctrl+f.