Miranda is an interesting one. Her default ME2 and ME3 outfit is pretty daft.
This is (just about) ok for mooching around the Normandy (although a size bigger would have helped her arse out):

However her alternate armour has quite a few advantages in my opinion from an immersion and design point of view.
Seems more fitting for some of the extreme environments:

Fits in better when compared to the other squaddies:

Makes her look pretty badass when required:

And is still capable, for the 12 year olds amongst you, for a bit of Massively approved fan service:

Shame they went back to the other version in ME3 (and carried on with the arse cam). Although I do prefer the alternate version that was done for her:
