the thing with mari, imo, is that she was more outspoken, great sense of humor, know how to present herself, and doing more things before and after her resignation, so she can find things to do that doesn't really involved singing. but i would also like to see her re-emerges as a singer, she is after all, a "variety idol."
...But with Miki, she doesn't do much except sing and dance. rite? i know she have regular appearances on radio show, like Yantan and her own, DokiMiki Night. However, although she great to watch and listen to, and good at presenting herself in a way, just not how most other people would. i dunno if she can do anything else except sing and dance, and she is one of the best in MM/H!P. so if she were to ever resign/graduate from MM, which she will, if not now, within a couple of years, she'll probably have a better chance to continue her solo career and GAM soon after the grad/resignation than mari does... considering she really can't do anything else, that is, if H!P/UFA decides to keep her...