In my experience, testing is (across the entire release cycle) often more buggy than sid, especially as it will get scant detailed attention in, say, the first year after a stable release. Using testing (for me) is usually just another annoying speedbump too - for example, one's issue is usually fixed in unstable and you are "just" waiting for it to migrate but it won't due to some boring, unrelated reason about 7-dependencies deep that might take a week or so to be resolved...