I had both and have tested both. I can't do you a comparison video as I have sold the EHX Magnum.
Basically here is my opinion:
EHX Magnum
Pros
- Cheap
- Small and lightweight
- Loud. It is loudest through an 8 ohm load, and is less loud through a 16 ohm load. For me with an 8 ohm V30 2x12 it was loud enough for rock band rehearsals.
- No fan noise
Cons
- Some people have had reliability issues. I didn't, but there are some reports of people having issues.
- Much less bass at high volume than the Matrix, in comparison the higher volume tone is noticeably thinner, also at high volume it is not as dynamic. It is loud, but it is 'shouty' compared to the Matrix which sounds 'big', if that makes sense!
- Less tidy (I prefer having everything in a rack personally).
Matrix GT1000FX 1u
Pros
- Lots of headroom
- More versatile. It can handle stereo patches properly, it can handle two different cabinets with different ohm ratings, each cab can be set at an independent volume.
- A noticeably bigger tone than the Magnum. More bass, 'wider' sound and more dynamic at higher volume (due to headroom).
Cons
- Much more expensive
- Bigger and requires rack space
- Fan noise. Though in practice this is not an issue IMO, I can live with it at home and at band volume I never ever hear it.
Hope that helps! IMO if you have the money go Matrix, if you just want something cheap the Magnum is good but not as good as the Matrix.