First I've used PNG's for my PictureMarkerSymbols. I'm not quite happy with the drawing quality, they look kind of pixelated.
Now I'm thinking about changing to SVG. My first tests showed much clearer symbols. But drawback seems to be that export to PDF and PNG doesn't work anymore. Also, it seems to me that it takes more time to build the map, and I'm getting timeout errors now and then.
Is anyone experienced with SVG's for PictureMarkerSymbols and knows about the drawbacks?