Best MC / MI under $500 with slide on stylus guard

I'm getting my new Rega RP6 tomorrow and need a cartridge. I like the slide on stylus guard like the Ortofon MC-3 turbo I had on my Pro-ject Xpression, but it can run a little bright at times. Is there anything else to consider? I've been told the a Rega tables / arm like higher compliance cartridges.
Has anyone done a 3 way comparison of the MC-3 turbo, the 2M blue and the Soundsmith Otello?