Well, this is just my opinion, but I think the Hall, Room, Plate and Spring algorithms are excellent. The EQ works very well to make them as warm as I want, but what really helps is the independently variable decay times for highs and lows. It's almost like having 2 separate reverbs (and DualVerb does exactly that, if I can't get what I'm after with any of the above). For instance, I have several presets whereI have a longer decay on the highs to give me a nice warm room sound that fades into an airy halo. I've also got a few presets with the opposite, where I get a bright tiled room sound that opens up into a cavern as it fades. The midrange EQ works great to either add body or make room for the guitar, making it as transparent as I want it to be, too. I've also got a small room preset that I leave on most of the time. I can't really tell when it's on, but I sure miss it when it's off. None of them step on my basic tone or get in the way when I'm playing fast.
What really impressed me, though, is trying to replicate the actual spring reverbs in several of my amps. I've been able to exactly replicate (not just close but dead on) the reverb from my Fender Deluxe Reverb, Fender Tube Reverb, Mesa Mark IV, and Marshall DSL. I'd flip back and forth between the amp's reverb and the Space, making adjustments until there was no difference. Then I asked several friends to tell me, without watching, which one was the pedal and which was the amp. Nobody could hear any difference between the Space and any of the amps.
I don't have an MPX1 to directly test against, but I have no doubt that the Space could hold its own against it. I do have several TC Electronic reverbs, both rackmounted and computer-based (studio plug-ins). The TC's are good, but the Space sounds better to my ears. I've also been using the Space in the studio and it's not quite (but almost) as realistic as several convolution plug-ins I also have, but it seems to fit into the mix better and adds something more… ?human? ?magical? ?organic? something… It just doesn't sound as ?surgical? ?steril? ?dry? ?generic? The only thing that comes close to the Space is the UAD EMT 140 Plate plugin, but that's not really something I'd want to use outside a studio, and even there, I've sometimes preferred the Space. Really makes me want an H8000, but I digress…
Anyway, all that's just my opinion, but I hope it helps. For my guitar rig, I haven't heard anything better that didn't also say Eventide on it.