I see what
@Lacius is getting at.
Sx os AFAIK doesn't do any checking afaik, and also of course has sign patches. Which means the xci loader is likely unsafe, if I had to guess. (since why at run time would you check the xci? Given the fact that xci's can be mashed with updates and dlc. It's not super far fetched of the "possibility" (likely exists somewhere) of someone maliciously injecting code into a xci)
while with a nsp, it's still possible but, afaik, most installers do check, and will not allowed unsigned nsps unless you change your configuration. Which for a unsigned nsp to exist, it has to be modded/unsigned. This gives the user a chance to prevent malicious software from being run since most, if not all installers will prevent the installation.
End of story regarding security
regarding format vs format it's .3ds 2.0
For the most part, in nearly every circumstance (unless... your using gateway still... jeez) you would install a .cia, or convert the .3ds to a cia.
with xci's it's the same story. For the open source custom firmware and homebrew, we use .nsp, and afaik there are tools to convert .xci to .nsp
and the downsides of the .nsp format have disappeared. aka the "double install" or where you have to put the game on the microsd card, and install the game. With goldleaf now existing and allowing a direct install. that really isn't as much of an issue. Also tinfoil exists so... Not going to say more about that. Which really kinda makes "xci being faster to play" not matter as much.
the only advantage of xci at the time, is running the game from a hard drive. Which, while an option. for those who tend to use their switch in portable mode or half and half (aka 50% tv, and 50% portable mode) then really it's a hindrance or quite useless. And also makes the switch whole concept of, well, switching, pointless.
If you fall under the really strict camp of "never taking switch out of the dock" and also owning SXOS. then yeah, the xci for the time, strictly for sxos's feature of xci loading from a hardrive. Is better.
This is basically the two arguments you had between two different people (I didn't make a mistake with the summery did I?)