I don't really see it as obsolete, I use emuNAND (and MenuHax Loader, which is outdated, but works just as well in booting up a menu just like A9LH does) for various things, such as testing and debugging games. A9LH might be something that can be used a lot, but I would be weary of something that modifies the NATIVE_FIRM section of the NAND to boot onto the exploit directly. If anyone accidentally updated their console to any future firmware that would be released, there's a potential that the update could have variables in it that alter any data in the NATIVE_FIRM that has already been changed by the A9LH which can then render your sysNAND corrupted, resulting in a Bootrom errcode Blue Screen of Death. And if that happens, there's nothing that can be done, unless you have a backup and know someone that can solder and flash the NAND onto the internal storage chip.
But really, in the end it all comes down the type of method you'd like to use for running Homebrew or any games that you have or any ROM hacks that you'd like to test out. If you really need to test out things on various firmwares, then using emuNANDs so you can backup your NAND incase anything goes wrong without having to modify the sysNAND itself on it's internal storage chip, so it provides a safe zone for testing stuff and checking newer firmware versions.
But if you're really just using the 3DS for games and Homebrew, then perhaps sysNAND would be your choice. The NUS CDN updates can be blocked through the CFW loaders anyways, providing that they're actively being developed. And A9LH can be applied to NATIVE_FIRM to make it load the CFW loader before loading the rest of the NATIVE_FIRM.