Right now, 4.x is considered the best firmware to have, because it allows you to do everything. I disagree with this--I think 6.x is the best firmware to have, it's just that the software needs to be adjusted for it. 6.x is the version that implemented the special savegame encryption key that hasn't been dumped yet, resulting in the loveliness that is savegame corruption and "Gateway Classic". This would be unnecessary if we could use 6.x SysNAND, because 6.x has that key active. The 7.x encryption key was dumped, so EmuNAND can use it for decrypting cartridges (that's what it does now). The reason 4.x is currently the limit is the exploits that are used by the 4.x loader are fixed in 5.0.0. The exploit to take over the System Settings application using a corrupted DS profile--the "mset" exploit--was not fixed until 7.0.0. It was other exploits that were fixed in 5.0.0 that broke Gateway previously. Now, we have alternative exploits. We and/or Gateway could use the "mset" exploit combined with "gspwn", "memchunkhax" and "firmlaunch-hax" to take full control of the system on 6.x with an identical startup user experience just by changing the DS installer ROM and Launcher.dat. This also goes for any of those XOR pad generation tools. I think that A Link Between Worlds, a very common game, has firmware 6.1.0, if I remember correctly.