If we're talking MiniDV here, than as long as the bits make it from the tape to the computer, you get the exact same file between LP and SP -- they record the exact same quality. The rub is that the margin for error when running at the slower LP is less, so if anything if off at all, you can get digital dropouts, which can suck bad. The other thing is that using a different deck than the originating camera to capture the LP tapes can result in problems during capture. It is mainly for these reasons that SP is much more preferred -- less chance for dropouts, higher likelihood tapes will last longer for archival, and higher likelihood that they'll work with any deck you put them in. If you really, REALLY need the extra 1/2 hour without a flip, or you have no extra tapes, then maybe, but otherwise I'd personally stay in SP mode whenever I could. That said, LP mode captured from the same camera without dropouts procudes the EXACT SAME quality as does SP mode -- so that's something to keep in mind.