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.
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
Cartridge loading is the act of putting a resistance (sometimes, a capacitor and a resistance) in parallel with the cartridge, such that the cartridge is driving the load.

We provided a cartridge loading strip on the back of our preamp for this purpose. Some preamps employ a second RCA connection in parallel with the input- you put the resistor on an RCA connector and plug it in.

Other preamps have a switch with preset loading positions. Still others use tiny little jacks mounted to the circuit board in the preamp.

Some phono preamps have no provision. Then you have to come up with something to make the connection.