Definitely bullet points. When people have a stack of CVs to go through, they don't read, they skim. Bullet points and appropriate use of whitespace help guide the eye to the bits you need them to take in (and even better, help them easily get past the bits they don't feel are relevant to them right now).
It's much harder to see the salient points when skimming solid chunks of text - and as your next victim isn't going to work harder when there are fifty more (or even two more) CVs to get through, it probably won't see what you want it to see.
Furthermore, places that use keyword searches on CV databases might have comparatively unsophisticated algorithms for ranking results. As bullet points promote a terser, more succinct style, it may be more likely that relevant terms are seen as being related by such an algorithm, thereby increasing the chances of your CV bubbling to the top of the results. (I have no evidence for this, it's just conjecture on my part.)
Eyetracking research has shown that, when people are browsing the web looking for stuff (as opposed to reading a specific article they've found through browsing) they also skim read in quite specific patterns. Some suggestions in articles about effective ways to lay out web pages can therefore usefully be applied to CVs, given the similarity in reading processes. Here's one example - it's about
landing pages on e-commerce sites, but much of what it says can be applied to CVs.
