I owned both, the Screamer and the TT.
Screamer is a fully equipped amp, with the Z5 you have 2 channels, boost for each, 2 switchable volumes, switchable reverb. It also has parallel/serial loop, compensated speaker out and 50W power. I mean that's a lot of stuff to have ...
TT is one sound (howver quick access with 3 potis and many different tones in that box).
For me the Screamer is an amp that you will like in the shop, it's got that impressive, but rather superficial, kind of compressed drive sound. I got some nice tones out I gotta say though, but in a band context it was never right for me, either too trebly or not audible.
The Orange is more of an addictive thing. It's the kind of amp that you can't put down the guitar once you start playing. When I'm playing i am constantly touching the settings, like I do the pots on my guitar, it's so easy to use and has the right in between compression and openness. Absolutely love it! It seems and is expensive for what it's got, but it's just sounding so damn great, on any setting, at any volume. Also in band context, it cuts through the mix like a wet fart through your white panties.
Best would be to have 2 TTs, one set for clean (master and tone on 10, loudness adjusted via the gain pot) and one for drive and A/B between them.
