Ask HN: Will webfonts ever be good enough?
How do we get webfonts to have all the benefits of system installed fonts with none of the downsides?
Answering your question, i think is not possible to get the benefits from a webfont, but one possible solution for your problem related to the downsides is to ask the visitor to install the font required, but it would be not practical.
Having an image for a logo often consumes less bandwidth than a web font (because there's a lot of CSS and a font file involved with a web font). SEO shouldn't be a problem if you use the "alt" attribute in the image tag.