moving coil vs. moving magnet question


As someone who is just getting back into the whole "audiophile" thing, I'm wondering what kind of cartridge to get. My Rega P3 with Grace 727 tonearm presently has an old Supex 900 low output moving coil cartridge that I'd like to replace. I use a PS audio step-up for it, but wonder whether I'd be disappointed if I went to a MM cartridge, e.g. a Shure V15v. What's the sonic difference between MC and MM?
stmike
The Grace is a good medium mass tonearm, the PS audio is probably a good step up still. I'd try a Dynavector, a Shelter, or an Ortofon. What's your price range?
I didn't want to go much beyond the $300 mark, as I'm buying some other new equipment as well. I figured some of my old equipment has been around here for quite awhile, and a change is always fun.
The info in this thread is great, especially that from sdcampbell. I recently posted a question with regard to the MM stage in the McIntosh MA6900. (probably on the wrong forum) I have recently purchased the mac and was wondering whether it would better to buy a new mm cartrige or use some kind of step up device so that I can use my existing Audio Technica OC-9. I am currently working abroad and do not have the turntable with me at the moment (Aplhason Sonata with HR100 arm) I am reliably informed that the phono stage in the mac is pretty good quality, would using a step up device with an MC impede the performance of the macs MM phono stage ? If you guys think it would better to use an MM what do you advise ? One guy has said that the clearaudio vituoso is a good bet also that the Ortofon OM-30 is a good cartridge.
For those who want to pursue the topic of MC vs. MM cartridges a bit further, I suggest you check the Audiogon archives. There have been a number of threads on this topic over the past 2 years, and the various threads should answer any questions you may have.