I have been using Kata bags for a while now. To haul my lighting gear, I was using the Kata OC-88. However, I found that it wasn't quite long enough to fit light stands or a portable backdrop. So, my photographer-husband, Andy Dunaway, did some research and found a good fit for me - the Kata OC-97. It's long enough to fit two of my Manfrotto Stacker Light Stands, an Elinchrom Rotalux softbox, an Elinchrom Quadra Ranger pro set, some Lastolite Tri-grips, five Nikon SB-900's and more.
I still use the Kata OC-88 for my Nikon SB-900's, rechargeable battery hubs, Nikon SD-9's, Lastolite EZYBOX softboxes and tri-grips and a bunch of other gear. The up side of the OC-88 is that it is lighter and the up side of the OC-97 is that is longer. So, it's really all about what purpose you are using the cases for and how much you want to haul.
If I wanted to, I could pack a third light stand, more tri-grips and another softbox. But it does get really heavy. Both cases have wheels and that's a big plus. However, someone has to throw the bag in the car. Luckily I have my husband who does the heavy lifting for me. If you are doing this on your own, you should be more aware about how much you pack.
I put together this little video, so you can see how I pack my gear.