Hi
Sunnyserendipity;
nelie hit it right on the head - reps vs. weights actually target different aspects of your muscle development. So really, the answer to your question depends on what exactly your goals are.
There are a few threads in the weight lifting forum as well right now, discussing different rep/set patterns for different goals and how muscle/strength develops. In terms of healthy muscle/connective tissue development, a 'bit of everything' tends to work quite well.
To add to what
nelie said: strength has to do with your muscles contracting
with more force, whereas endurance is about them contracting
for longer. The two aspects actually use different metabolic pathways in your cells (aerobic vs anaerobic). Mid-high rep schemes (ie. ~8-15 reps for women) will also cause some hypertrophy (muscle growth). Low reps (3-8) aim closer for strength, and higher rep sets (15+) develop endurance.
I like to think of strength as picking up a toddler vs. endurance as holding the kid for 2hrs.
I'll also mention for
Mad Donnelly: A) kudos for not worrying about looking like a bodybuilder! and B) take a look at your training progression, and maybe ask yourself how much direct ab/core work you actually want. While women don't put on upper body muscle as quickly as guys, we're still very capable of growing, especially in body parts that we work - it's very possible that you could increase your waist circumference from ab/oblique exercises (not sure if that's a concern/goal, but it's worth mentioning just in case
).