The output impedance of the two amps is different. OTL has a LOT of negative feedback which lowers the source impedance to like 0.1 ohms. That will really affect some speakers that are designed with solid state amp in mind, like Paradigm/Anthem.
Normal tube amps usually have less feedback, higher source impedance and weaker damping. Some people like this as warmer, softer sound. SDFR speakers sound better with less electrical damping. Nelson Pass wrote an article on First Watt website about this, talking about his current source amps, which have no electrical damping at all.
http://www.firstwatt.com/pdf/art_cs_amps.pdfThere may be other articles there, this is the first hit I found on goog.
When I was building boxes for my featrex D5nf FR drivers I built a LM1875-based current source chip amp which made the SDFR sound very good. Stopped all the shouting they tend to do. But the 1.5ohm source impedance tube amp Manley Snappers were even better. But Cary SLI-80 was atrocious as were many normal voltage source solid state amps. It's a weird thing.