This list is incomplete. A good explanation is:
simpler
harder to change it without ruining it
solves more problems
less non-functional parts
more adapted to solve the problem(s) its aimed to solve
solves its problem(s) better
tells us more about reality/anything
helps more with other fields
has more implications for other problems; has more reach
connects with more of our other explanations
better compatible observations/measurements we've made (hopefully consistent with all of them)
better structured/organized
less internal contradictions (preferably none)
less external contradictions, ie contradictions with other important explanations
easier to understand; harder to misunderstand
better designed to prevent people understanding part of it and then making mistakes
shorter
in a better language (or format, like PDF vs MP3)
more logical
more fun; more exciting
more honorable
more optimistic
most just; more fair; more practical
easier to remember; easier to abbreviate; easier to add detail to as desired
note that this list contains duplication. for example "harder to change it without ruining it" (which I'll abbreviate as "harder to vary") is a powerful criterion. it covers both "simpler" and "less non-functional parts". non-functional parts are easy to vary because you'll never break anything as long as you change them to something irrelevant. and excess complexity provides more areas where some varying might work. being hard to vary is also roughly the same as being well-adapted. the better adapted something is, the fewer variations would be beneficial.
note that none of these are guarantees. a very simple explanation can be false. an optimistic explanation can be false too. that's why criticism is always important. if someone gives a criticism explaining why in this case optimism is misplaced, then so be it; these are just general, rough criteria.
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