I've done both, but I have to admit I prefer to attempt to repair paintwork rather than respray as it can be both very expensive and unsatisfactory when compared to the factory scheme.
Once you've got lots of big chips in complex, multi-layer sections or rust has started to eat way under the paintwork, its time to make the jump and decide what the new coulour scheme is going to be.
With full reworks, Ive paid a couple of hundred quid for a single colour enamel and decal job and been seriously pissed off with the job and I've paid under 50 for a powdercoat and done the decals myself and been very happy with the outcom.
Touch-up jobs are very much trial and error and you MUST do them in daylight.
