would make more sense if this was in general..but here goes.
i never used realsoft but from what ive read ..it crashes a lot, and since realsoft tried to put in as many bells and whistles into this package....none of the features are really finished and are very buggy... some modelling/ rendering aspects could be improved.
the work that you can get out of it depends on who is clicking the mouse:)
as for mirai...quality wise..its way up there. its a very solid package ( the "you get what you pay for" saying applies here ). for modelling, you can do anything really, users that use mirai tend to do a lot of modelling of organic characters. but from what ive done...i can say that the package is not only made to do organics.
pic1 or pic2 or pic3( im still working on those ).
the thing that i find a little weird is that very few people use mirai to do character setup/ animation work.having an NLA system that is on the same level as the Softimage | XSI package. the character setup tools are also very well thought out .( i could tell you Tons of cool things that you could do with setting up characters in mirai ) and maya is almost finally caught up to mirai character setup tools with release 4 ( looking at the animation/ UI improvements on their website) only thing about mirai is that its got a relatively weak renderer., it cannot do anything but subd. and the requirements are rather steep ( on video card ) because unlike other applications, mirai uses multiple opengl windows, whereas other apps use 1 window...and subdivide it..
heres some pics of models done in mirai.
monkey
Vig
ken brilliants page
bay Raitt ( though his gallery hasnt been updated for a few years now.
heres some stuff i made
( err..still working on..)
old guy
younger guy
bending-oldie( notice how his belly is sticking out:)
and ofcourse you could visit my site in my sig 
hope this shed some light.
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-M-K-
ambient-whisper