cIOS based on IOS58 is rarely used.
it was mostly installed and suggested by guides written by users who didn't understand how cIOS worked, and decided to install lot of useless things. Mostly on the start of vWii hacking (Wii guides didn't suggest that one), I couldn't count how many random setup users suggested to be the first to get vWii hacking working, without understanding the console only loads one IOS at a time and having 3 wasn't why it worked. *let's fill the console with random unneeded shit ... oh it works! that's the way to do it!* you see the thing?
base58 is slower than base57 for USB read access, and has many non working games (it will freeze or randomly black screen while playing). only very few games really need that one.
I think it was either chosen because of increment value 56>57>why not 58! (most likely), or because it contains the official USB Module from Nintendo to init USB devices (very less likely, noob didn't even know that).
Do not install it if you don't have a need.
you only need one cIOS, base 57 is usually fine for most games.
if you play lot of guitar hero/rockband, then maybe go with base56.
I started suggesting base57 because a majority people wanting to play Call of Duty Modern warfare, which works only with 57, and had enough of all the newly created threads asking why CoD (and recently Just dance 2020) didn't work! as most other game work also with 57, I decided to go with 57 by default. To my knowledge only spyro (with the NFC portal accessory) needed base56 and less users have that one, but I only recently learned about all the Guitar Hero games needing base56 (like.. last week!).
Look here for the "required base":
https://wiki.gbatemp.net/wiki/Wii_cIOS_base_Compatibility_List
this lists only problematic games, the one which work with only one specific base, either 56, OR 57, or neither.
games working fine with 56 AND 57 are not listed as they are not problematic, and you can go with any single slot cIOS setup (either base 56 or 57).
usually, I only recommend this :
slot249: d2x v10 r52, base57
If you prefer USB read speed, go with base56 instead, but you might need 57 for Cod and Just dance.
USB read speed wise : 56>57>58
if you really need the second base, you can install it in slot250, and change your loader or game settings accordingly when needed. I recommend you only set the "other slot number" individually in your game settings, that'll prevent you to change your main loader's IOS setting every time you play a different game.
