I've always been very happy with my KR Multicase boxes and bags. They provide great protection, are modular which saves money in the long run, and storing the miniatures which are not currently in the shell bag in card boxes rather than loose trays adds an extra layer of protection to the collection around the house.
And while my Kaiser 1 and Kaiser 2 bags have always been perfect for transporting games like Flames of War, 40k, or Saga around, I felt like they were a bit overkill for Guild Ball's paltry model count.
What I wanted, then, was something that would let me take advantage of that small model count by packing the smallest, lightest, but most effective storage solution possible. While I must admit, I did not find, from any vendor, precisely the case I wanted (12 figure capacity, hard sides, minimal size possible) I found something very close with my old standby, KR.
What I ultimately settled on was a Kaiser Half shell and two KRQ quarter size card boxes filled with SM47 trays (a quarter-size, 15-cell tray). This turns out to be a very flexible choice for Guild Ball. I went with the Kaiser rather than the Aquilla because the Kaiser is slightly larger to accommodate card boxes inside, where the Aquilla just holds foam trays. I wanted to have that extra rigidity, which comes at a price, but my miniatures are priceless, right?
Starting small, I can always carry just the KRQ card tray. Sturdy enough to prevent damage from incidental bumps, it's nonetheless the size of a large book, fitting easily into a backpack or briefcase. You do sacrifice a little security with the card box alone, but it's enough piece of mind to allow for all but a determined attempt to crush it.
Moving up, the Kaiser Half shell gives me a couple of options for going out with less than my whole miniature collection in tow, and does so in a size that's really quite handy, feeling like little more than a lunch box.
One convenience is that the tackle box that I use to keep all of my assorted playing gear (dice, tokens, templates, etc...) happens to be just slightly smaller than the KRQ box. This fortuitous fact allows me to carry up to 15 minis and my gaming supplies inside the Kaiser Half - which is the perfect arrangement for a day of gaming out at the store or a friend's house. Plus, If I needed to bring along 30 miniatures but still didn't want to pull out the Kaiser 1 (maybe because the Half fits in a backpack or suitcase way better) I can always toss both KRQs into the Half and go.
Like I said before, you pay for what you get here. This particular arrangement, which pays a premium to move up to 2 KRQ cases rather than the one half-size card case that comes standard, plus the pricier "custom" class tray weighs in at a shade over $100. (in retrospect, I would have been fine with F2H trays with a couple of cells merged to hold big guys, which would have shaved a few dollars off).
To quote Ferris Bueller - If you have the means, I highly recommend it.