I think the fact that with MMP.... Of course, if you have STV you do not have that, and I think STV is a reasonable option for Canada, or any country as well.
With MMP you do have the fact, and I would not consider it a problem, that you have two different sets of legislators. In practice, in both Germany and for a shorter time in New Zealand, this has not caused a big problem. A party still tries to put people on the list so that the list is geographically dispersed, and so in many cases in a particular district or a riding, as you call it in Canada, you will in fact have two representatives from that district, one elected from that district and one elected from a list. They may well be representatives from two different parties, so that the people can feel comfortable with at least one of these representatives. This depends, of course, on how the parties manage the process of putting together the list, but I think that, on the whole, is the way that parties have tried to do it in Germany and New Zealand.