Benefit of low output moving-iron Grado ?

Hi all,
I'm considering a cartridge upgrade from a high output (5mv) Grado Sonata cartridge to a moving-iron Grado Master cartridge, either a low output (.5mv) or a high output (5mv). If I choose the low output version, I would have to drop an additional $250 on a phono card for my Exposure amp, whereas I've already got the high output phono card installed.
So my question is....
a) is there a sonic improvement in low output cartridges, or is it more a matter of taste
b) I hear a kind of "shrillness" when vocalists use an "s", and with other very high frequency sounds.... is this shrillness reduced by using a low output cartridge?
c) does Grado's moving-iron type of cartridge have properties unlike moving magnet or moving coil that might be relevant to the other questions I raised?
Thanks in advance, and I always appreciate this forum.
You might want to experiment with loading. We had a ZYX Universe that was very nice, one day the needle just decided to let go of the cantilever and that was that.

So we installed a wood-body Grado we had on hand. Its 5mV. It was also a little upfront/in your face compared to the ZYX (we are running a Triplanar which easily tracks either cartridge). However being a high output moving magnet, they are sensitive to loading. We've used 10K as a loading value in the past, and that seems to work well with this one too.

Funny thing, if the arm really *can* track the cartridge, you have it set up right and loaded right, you really don't hear big differences between many cartridges. Miss one of the caveats above though and its a different story!

IOW we're not hearing a big difference between the two cartridges other than output. Loading in this case was the key as the Triplanar was not the variable.
I've been lurking around this thread as I too have a Reference Sonata and felt it was very brash, comparing it to my Zu DL103 on my other table. Tried the 10k loading and it did the trick. Much more laid back but did not lose any of the sparkle.
You don't get hum if set up right. If you have a Rega, you might get hum because the motor is not grounded. Easy enough to fix.
Not sure what loading is... or if my phono card is capable of being set to different loads (if loading takes place in the phono stage, that is). Could someone inform... thanks