Assuming as your username suggests, you're in the social sciences, you should apply for both and anything else advertised anywhere. The competition for both is likely to be very high. In my social science field, you probably need 3-4 good journal articles, teaching experience in terms of having led your own modules, plus increasingly evidence of non-academic research engagement and preferably the beginnings of a track record in grant getting, to get shortlisted for a permanent lectureship, as there will be people with all this applying. They aren't much bothered about how you've gained the experience. So if you were lucky enough to get offered both, then you'd need to look at your c.v. decide where the weaknesses are and which post would offer you the chance to fill in the gaps. You won't get much teaching out of a postdoc, and you're unlikely to get much if any research done on a temporary lectureship as they are often a bit exploitative.