That's correct. In high gain mode, the HT100 reminded me of a DSL. Blackstars are darker amps than Marshalls. I was trying to get the Blackstar to do the Marshall thing and although I came close, it didn't work out. I wanted to have the bright crunch my DSL had, but the amp is inherently dark and trying to make it a brighter amp just made it sound sharply present and uneven.
Blackstars have a tighter, dryer feel to them. Marshalls are a bit more responsive. However, the HT100 had better definition. I think that if I had one now, I'd use Eminence Wizards or G12T75s and swap the stock tubes with something a bit brighter and clearer.
I think the Marshall is punchier and when you mute strings and strike power chords, it's a bit more stinging in a good way. The Blackstar had a better growl and not as buzzy, but doesn't have the same kind of crunch.
My HT100 had a digital reverb and the DSL had real reverb. I think the Blackstar reverb is pretty good, but I really liked the reverb of the DSL. Even though it's not a real strong reverb, I never felt like the reverb ever got in the way of the tone or other effects. The HT100 has a little more effective EQ. The DSL has a deep switch but you can't control the resonance it creates. The HT100 has more tonal options.
I liked the clean channel of the DSL more than the HT. To me the HT clean channel is very good, but at the same time is a little sterile in comparison.
I have compared the HT series (made in China) to the Series One (made in UK). The Series One is in another class and to me would compare favorably to Marshalls, but they're also in another price range.