As a rule, I use pop-tops. Occasionally, however, a screw-top sneaks into my rotation and I end up figuring it out only after I've opened the bottle to drink it. Using just those sneaky bottles I've opened as a metric, I have had about a 75% success rate with them. For my own purposes I'd rather eliminate them entirely than risk a 1-in-4 chance of getting a crappy beer. If I were bottling a 5 gallon batch in screw-tops, that would be a whole 12-pack down the drain.