It is often said that Tubescreamers of any kind do not work that well with transitor amps. Tubescreamers can give valve amps a natural boost, depending on how you dial in your sound. Simlar results can be achieve when you use a transitor amp. Most Tubescreamers will give you midrange boost, but this sound may be just what you are after.
Does a tubescreamer sound very different through a valve amp? No, but a valve amp will sound better in general, maybe that is why some players think it is better to use a Tubescreamer through a valve amp instead of a transitoramp.
A Tubescreamer works its mojo on almost any amp whereas a pedal like the Boss BD-2 may not do that and may prefer certain amps.

Happy playing and hope to see you soon again,
Eddie