I started buying AT cases before CTI became available. I have the HobbyLine for E to G, the 29/180 & 29/240 for H, and the 38/240, 360, 480, 600, & 720 for the full H thur I range. Of course the 720 is for the baby Js, but for most Level 2 I go with the 54/1280 & 1706 and CTI 6GXL with or without spacers. Those case allow me to fly the full range of motors from E to small L. I can't fly every reload, but enough to keep me entertained!
The way I see it, there isn't a lot of advantage in getting the cases on either extreme end of any of the sizes. The 29/360 can be replaced with a lot more reloads in the 38/360. The 38/1080 can be replaced with more reloads in the 54/1280. The same applies when looking at the low end like the 29/60 & 120 cases can be replace with the HobbyLine, the 38/120 by the Hobbyline or a 29/240. It's just my thinking, but I won't get one of the cases on the ends of the ranges unless there is a specific motor I just have to be able to fly. I haven't come across one in the 8 years I've been flying HPR, but you never know. For those that do have that one reload they just have to fly, by all means, get the case! Enjoy!