Update August 2015: check “scaled”- based fast SVG rendering on top of Leaflet here
Updated May 2014: check leaflet Canvas test here, SVG with d3 here and WebGL here
Thesis on Canvas and Open Layers (August 2010) “Evaluation of HTML5 for its Use in the Web Mapping Client OpenLayers”
OpenLayers with Canavas (partialy deprecated) http://trac.osgeo.org/openlayers/wiki/Future/OpenLayersWithCanvas
SVG vs Canvas comparison by Jeffrey Warren from : http://unterbahn.com/2009/08/svg-vs/
“Well, SVG doesn’t scale well to large numbers of objects, but Canvas doesn’t
scale well to large screens”
“SVG performance degrades quickly (exponentially on Safari?) in the number of
objects, but Canvas performance remains at a near-constant low. This makes
sense, since Canvas is just a bitmap buffer, while SVG has to maintain
additional references to each object that it renders. Also, though not pictured,
note that performance in clearing an SVG element also decreases in the number of
drawn objects.”
[UPDATE] PDC2010 video by Patrick Dengler : http://videoaz.microsoftpdc.com/vod/downloads/vod/CD53_PatrickDengler/CD53_PatrickDengler_PDC_WMV_High_1280x720_2500k.wmv
∫ ∪ ∧∴ ∋ ∈ ⊇ ∧ 
Pingback: SVG map sample and Canavas in OpenLayers « Geospatial Haiku « svg
Yes, this is the main difference between retained mode rendering systems and immediate mode systems — identity comes with a cost.