Which is better RedNand or arm9loaderhax?
TL;DR: My personal preference goes to A9LH (and I think most of the Tempers will agree), but RedNAND and A9LH are not the same thing at all. If you'd like to read a bit more, I'll proceed to explaining a bit in depth, while trying to be no too technical or confusing.
Let's start with clearing up a few terms here:
SysNAND: your actual system that is installed on your console, and on which the console firmware runs
EmuNAND/RedNAND: both are pretty much the same, and are a copy of your SysNAND that is installed to your SD card, and on which runs a custom firmware
Custom Firmware (CFW): a modified version of the console firmware, that lets you, among other cool things, install and run unsigned applications and games
What I meant by RedNAND was that basically you will have:
• Your SysNAND downgraded to version 9.2, which is a version that contains system exploits that enable us to "control" the console a bit deeper
• An EmuNAND/RedNAND, on which you can freely install games and homebrew, and that you can update to the latest version while still having a hacked console
The downside of this is, while it is faster to setup than A9LH, the boot time is pretty long (you technically have to boot to SysNAND and then to RedNAND). Also, if you come to update your SysNAND from 9.2 to a more recent version, your console will lose access to the hacks and the EmuNAND.
Now, arm9loaderhax (A9LH):
It is a system exploit that gives us control of the console very early during boot, and once it's installed, it's there forever (unless you explicitly overwrite it).
It IS a bit longer to setup than just setting up a RedNAND and booting to it with a custom firmware, but it gives you:
• Very fast boot times (6 to 8 seconds): it boots directly to a custom firmware on SysNAND
• You don't have to keep a RedNAND on your SD card, so you win 1 to 1.2 GB on your SD card
• You can update your SysNAND to the latest official version and never worry about loosing access to the hacks
• A protection against bricking your SysNAND (= rendering it unusable). Since A9LH is available early on boot, you can make backups of your SysNAND and restore them, so even if you screw up you can flash a backup
You might also want to check the
FAQ of Plailect's guide.
EDIT: in the FAQ:
Luma3DS is the most popular custom firmware nowadays
A
CIA is a file that contains a game or an app and that you can install to the console