What are the appropriate words for these definitions?

1)) ease of use, comprehensibility of the interface, comprehensiveness of functionalities, streamlining of the options. Radically clutters up the code and makes it much more error prone.

2)probability of the program not crashing while you’re working. Needs as little errors as possible, hence needs more streamlined code. Further proof of this is that server programs generally don’t come with a graphical interface, because they need to be always up and working with as little maintenance as possible.

The reason I’m asking is, I wrote in a thread: “Doesn’t reliabilty increase usability? I mean if people find something unreliable they would be less inlcined to want to use it, no?” I got the answer “no”.