The true difference is that RajNX allows users to edit config files and adjust it. Rei designed ReiNX to be complete out of the box.
You seem to imply that RajNX requires manually editing a config file to function, which is simply not true. Both work perfectly and are completely safe "out of the box", but RajNX has a menu available in case you need to make changes, which IMO is simpler than deleting/renaming/moving files. To change the boot options for Rei, say to disable LayeredFS or the NOGC patch, you either need to use separate hardware or a homebrew app like NX-Shell. This isn't a big deal, but objectively declaring one method as easier or safer or more beginner friendly than the other is ridiculous.
As for reduced telemetry, RajNX blocks a specific sysmodule from running and collecting potential data for a ban. Just like domain blocking, whether this reduces your chances of being banned or not is purely speculative, and I don't know enough on the matter to give an opinion.
RajNX also gives the ability to customize the shortcut to the homebrew menu, which I believe is still a unique feature. I prefer having to hold R to launch the menu to reduce the chances of my non-technical friends from messing with something they shouldn't, and while this is a very minor preference, me and a couple other users asked for it, and Raj implemented it in about a half hour. I was impressed, to say the least.
But really, these are very minor differences, and I contend that the bigger difference between the two is the people behind them. Rei is great, but at least one of the main developers for ReiNX is, let's just say, a not very nice person, and I prefer to avoid running software he is involved with.