I suggest you get the biggest bag you can afford. You ALWAYS get more models
I got this a few months back (the backpack) http://www.krmulticase.com/cases.aspx?system=WYD&army=MFX
and it is great fitting 60 x 30mm, 8 v 40mm and 6 x 50mm at the moment although the pick and pluck foam allows any variety of 40mm and 50mm depending on what you need.
It also fits the large rulebook, crossroads, all my tokens / counters, tape measure, wooden box that holds my cards and the kitchen sink so only need that backpack for everything I ever need for multiple crews and accessories. I highly recommend
But also depends on your budget I guess.