It's a very good question you asked.
No system is perfect. If we could find a perfect system, every country in the world would be using it right now. All systems have their pluses and their minuses, and the big challenge that's facing you is to try to figure out a system where the pluses outweigh the minuses, or they do the things that you want them to do.
Take first past the post: strong, stable government, local representation, great. Disproportionate? No. Well, you know you give up one thing.
If you use tier PR or list PR, you get perfect representation, all votes count the same and everything, but you don't have any local representation.
I could go on and on. There is a whole list of different things that you want. You have to balance it.
I hate to keep plugging my system, but if anybody has ever read this white document, you'll see near the end of it there's a report card for EVC in which I list from A+ down to B, the lowest rating. I don't know if anybody ever read it, but I think it's a good system because it does have a lot of pluses and not any minuses that I can really think of, except for the problem of expanding constituency size, and if you're going to have a mixed member system, you're going to have to do that, unless you want 500 seats.
You have to balance. It's a question of balance.