Well, the beauty of fastboot3DS's chainloader is that 1. You can use button combos, rather than just a single button, and 2. It can boot from multiple places. Luma3DS can only chainload from the SD or CTRNAND, but fastboot3DS can chainload from SD, NAND [CTRNAND], TWLN [TWLNAND], TWLP [TWL PHOTO] as well as firm1.Yeah, it seems super nice. Once I dump my cartridges and/or dump NAND and other system files, I don't tend to do much else with the chainloader menu. I'll have to dig deeper into it, but I do most file operations on my PC since it's not super inconvenient. Is there much else I'm missing out on?
It allows for much more flexibility in general and even sports loading A9LH payloads (.bin payloads, instead of sighax's .firm) as far as I can tell.