Tubes are slower, compared to SS. Last night I recorded a couple of tracks, using one tube and one SS, each one on a separate channel. I used a Fostex recorder. Then I imported the recorded tracks into Reaper. The SS track was right on click (I used the Fostex's Metronome while recording), and the tube one was consistently behind, a couple of milliseconds, maybe even more. I was slightly surprised, but then I remembered Pat Metheny said somewhere that he prefers SS amps, because tubes are "slow". Last night I understood what he meant.