This is cool to see some testing done for load speeds with higher size cards.
One thing I can say about the larger cards like 1TB, it might be useless for 3DS games generally speaking because of 300 title limit, but 300 titles is still a lot of space and then you can start piling on the PS1 games etc that are also kind of big now that this emulation is better, and those won't take up tile space. I still don't think 1TB will get close to being utilized, but 256, or even 400 might be reasonable for some folks I have to imagine.
After around 2 months, I can safely say that I would NOT recommend using such a ridiculously large micro sd card for 3ds purposes except in very specific use cases. At this point, I've basically turned my New 3ds XL into a very good retro emulation machine and rom archive, having downloaded fullsets of nes, snes, gb, gbc, gba, nds, n64, atari 2600, atari 7800, sega master system, genesis, sega 32x, sega cd, commodore 64, as well as partial sets of my favorite ps1 and amiga 500 games. As for my home menu, I've got every single 3ds game I'm ever going to want to play, all my favorite roms through vc injects that I wanted to run through official nintendo programmed emulation, for convenience or compatibility, all of the standard homebrew applications as well as some emulators, games and ports (including copying my old SRB2 installation folder with about 5gb of outdated addons that I'm very glad I archived), and some forwarded nds games that I want recorded playtimes on. I counted 186 titles on FBI in total, although I didn't bother to count the preinstalled and non-named stuff, though I'm sure some of them count... and I still have 560gb left. I am a software hoarder. I openly admit to spending way to much time downloaded and organizing games when the vast majority of them will never be played, but that's just my character.
The reason I don't recommend this, besides the price and besides the fact that the vast majority of people are not going to cram every bit of software they can get into creating the ultimate portable dual-screen machine like I have, is that there are actual technical issues that come with having a 1tb storage device on a gaming portable with drivers designed for probably a maximum capacity of 32gb (iirc, the retail maximum for 1tb micro sds). It wasn't noticeable at first, which is why I said in my og post that it worked faster than my 64gb, but as more space is taken up, the initialization time for the home menu is drastically increased. When major changes to the file structure (renaming and moving folders) or the addition of significant amounts of data are made, it can take upwards of 3-4 minutes to for the 3ds to boot. I don't mind this, as it quickly goes back to normal by the 3rd or 4th boot after that, normal being around 20 seconds, but I'm certain others will. Also, I have major problems with ds mode. I have to keep only about 5 or 6 roms in the default TWLightMenu++ folder, as going much above that (say, 10 or higher) will make the booting of the app takes over a minute, even when using the closing and opening the screens trick. Also when playing ds games with large file sizes, I suffer random crashes which are not remedied by any diagnostic technique, and I've gone through all of them, I promise. This is just a theory, but considering this did not happen or happened much less on my 64gb card, I think the random reads required to load the data in the time with drastically undercloaked processor causes the data to not be finished reading by the time the game expects, causing unavoidable crashes. I have weak corresponding evidence for this, since I was able to cause similar crashes twice in 3ds mode by changing the clock speed and cache through rosalina to OL3DS levels and attempting to play through ultra sun and ultra moon, though these crashes could be caused by many things.
Average consecutive write speed of large files is 32mb/s to and from pc to microsd, and 2mib/s when installing from FBI. When reading or writing many consecutive smaller files, the speed drops drastically to around 5kb/s to and from pc to microsd, and to somewhere less than 1kb/s when transferring files around through the homebrew file manager I forgot the name of now. The concecutive speeds were faster than my 64gb card, which was about 14mb/s to and from pc to microsd, and around 1.4mib/s when installing from FBI, but this was probably just from being a lower generation model, since the small file read and write time and even the random reads and writes tests I did, which I do not recall the numbers from now where drastically higher than the 1tb card.
like a 250 dollar kit back when DDR4 was Intel only