Core workout vs overall body workout

probably depends what you are training for. Like if you are training specifically to break the world record int he plank than probably concetrating on core would be the best bet. Otherwise, If you do a full body workout each week, not sure what it is looking like, maybe squat/bench on one day and deads/ overhead press another day, I think your core will end up being rock hard.

Yeah I'd say focus on full body strength training. Fit in what you can in 30 minutes. And change it up often so you hit all muscle groups at least once a week. Do a few sit ups when you get up in the morning. That's probably all you need.

I second this. For most people, heavy squats and deadlifts will do more for ab strength than most "core" workouts.

If you don't dawdle, you can get a lot of work in 30 minutes. Assuming you aren't waiting around for equipment. I'm a big fan of squats, personally. Works you a ton, in a very short amount of time.

People more educated than me say that modern wisdom is that low rep high weight is ideal for anybody looking for strength(period, no matter the athletic goals), the high rep low weight is for people trying to build mass/shape aesthetics, like bodybuilders. So if you subscribe to that, a few sets of low reps is awfully fast. No doing one thing for ten minutes.