Re: Engl Fans?
I don't know much about the screamer but I can tell you the Thunder has enought gain to shred with plenty and enought output to make you desire earplugs. So I think your decition won't a matter of tone, gain or output.
But if you talk about features I think the Screamer clearly beates the Thunder. The Thunder offers you 2 channels (crunch and lead are the same chanel but with a different gain stage) and a reverb. The Screamer offers you 4 channels, a XRL line out output to plug it to the mixing desk, a reverb and a bright swithch. But, apart from the XRL line out (which it is a great feature if you like home recording), the rest of features seems to be unnecesary. I mean, aren't 2 gain channels and a reverb more than enought? If the tone of the amp it is good that should be the most important feature.
So, I guess your decition depends on what you are looking for. The Thunder offers great tone with enought features to make it very versatile IMO. The Screamer goes one step forward and makes it a tweaker paradise...