The efficiency of the diodes and total light won’t change with the length of strip, they’re the same. It will be a product of the drive current we decide to run them at. They’re pretty darn good at 700ma, and don’t really drop off too much at 1050ma especially being mounted to the aluminum. One of those will be best bet. For example wattage can be the same for 4 1120mm strips at 1050ma as 6 strips at 700ma on hlg-185 series. Same line of driver different output current cost difference is exactly two strips. So $30 gets you about a 5% increase in efficiency. I have built them both ways, they work fine both ways, that will be entirely up to you.
I think the biggest decision in whether to go with short or long strip will come down to coverage. Are you more likely to have dead space along the 4’ walls or the 6’ walls? Once they’re built you can’t really play with your strip length. But you can slide fixtures in or out to kind of tweak coverage right?