As Dietz says, both have their uses. If you're looking for a guide as to which one to choose out of the two, then MIR offers a lot more besides just reverb but comes at a higher price.
One thing I would say about MIR that's almost counter-intuitive is how easy it makes making decisions. I use MIR on almost everything, and only occasionally reach for Vienna Suite. When I do use Hybrid Reverb, however (does anyone just use the Suite Convolution Reverb on its own anymore?), I find I am spoiled for choice. I go through every preset in the type I am looking for, and then try others just to be sure. I try tweaking most of the edit paramaters, and see if I can hear the effect on the sound, and then decide how I like it best (probably how it was to begin with).
Whereas with MIR, I drag the icon to the position I want on the stage (usually just touching its neighbours), point it at the microphone, reduce the dry/wet offset to -30, and I'm done. If I don't then like the sound, I'll of course change it, whether by rotating the instrument, moving it, switching the profile or character preset etc. But otherwise that's how I leave it. For a default setting, I like the solidarity of MIR, of knowing that that's how that actual instrument would sound in that position in that room, and so I have the confidence to use that 'reality' as a starting point.
You can still choose between MIR venues, mic positions and reverb times, but even then there are only 20ish venue options to choose from, and the audition feature on the load screen is really helpful. I think because you are constantly looking at the venue, too, when working on the project, its identity is more built up in your head. So I can think 'Teldex would be right for this' when starting a new project, because I am familiar with it from memory, or 'Maria Strassengel is too small, let's try the monastery' etc.
I rarely use MIRacle myself, as I have to keep the reverb firmly under control to work in my mixes, and I tend to treat any more ambient track needing more reverb presence as an excuse to break out the Mystic Spaces roompack (which I would recommend along with the Studios & Soundstages roompack as the two I use most). But it can be really useful for adding more reverb towards the end of working on a piece rather than redoing all the venue stuff, or for adjusting with automation as the piece changes.
MIR is very expensive for a simple reverb engine. For what the product actually is, however; a virtual recreation of real venues and visual mixing environment, it's an investment I've never regretted. If nothing else, for its authenticity: My recording is the sound of my music is being played by an orchestra largely made up of players from the Vienna Philharmonic, in the foyer of the Vienna Konzerthaus next to the bust of Beethoven, and while it doesn't happen in quite the manner people might expect when you describe it to them like that, not a word of it is untrue.
