For starters: I started on guitar, then focused way more on bass early on. That was 17 or 18 years ago. Short answer? I would do whatever I felt like doing.
The bass may make you more money and give you more musical opportunities, but...
The guitar will get you laid WAY more.
I think switching back and forth is a wonderful opportunity to grow your ear (and dexterity - whoops, that scale you were going for doesn't quite work that way when you get to the B string on the guitar!). Even a rudimentary knowledge of chord structures on guitar will put you LIGHT YEARS ahead of other knuckleheads on bass, and that's a fact. Come to think of it, I don't even know how the hell people get as far as they do playing bass WITHOUT knowing any of that stuff, and guitar is a perfect "gateway" to learning it.
Also, you are mistaken in thinking you'll just be "mediocre" by meddling with two things instead of one. "Sacrificing" practice time with one for the other is a lot different than sacrificing practice time for video games or other unproductive nonsense, see what I mean?
Right now, I'm in the Chicago Businessman's Orchestra (bass) and I'm in a unsteady, unmotivated wedding/bar/cover band (the gigs of which pay ironically well), but I still get asked to show up at campfires / parties with a guitar (and typically play for a few hours). I'm not the best at any of these things, but I'd never trade the time I spent learning what I know on guitar for more bass chops. No way.