I always was of the opinion that The Outer Limits was a lukewarm Twilight Zone. The Zone dominated. Still does. Morality plays with a twist. Rod Serling was great at that. Any opinions to the contrary and you'll be wished into the corn field.
I think that there may have been more sustained drama in The Outer Limits (I've got a full set of episodes I taped off air years ago but never got around to watching all of them).
The Twilight Zone had an "unusual situation" and maybe a twist at the end but not always a lot of plot inbetween.
That said, I'd probably turn on the Twilight Zone first if the two shows were aired opposite each other.