Ladies...LIFT HEAVY or do a million reps?

I've been lifting heavy, so I'm on the right track I guess. I would just like to see my arms with more definition... My stupid scale won't budge very much lately, thanks to a stupid plateau I'm trying to get through. Anyone have any good arm exercises in mind?

So I am looking to get some input from my fellow lifters out there. I bought a home gym and have been lifting pretty much every other day for about 6 months now. I can see a change with my muscles and body shape changing, but it's not fast enough or what I want. I can see my biceps when I flex my arms, but I would like to have more definition on the 'outside' of my arms. (When your arms are down at your sides, the 'outside' is the part others see.)
My question is this...if I want to get more results with my exercises, is it better to 'lift heavy' or is it better to 'do a million reps' of each exercise at a lower weight?
I'm also welcome to other ideas or hepful info as well. Thanks!

BOTH. change it up. Don't do the same thing over and over. I did just 10 reps, about 3-4 sets, of about 10 exercises for years and years and it gave me a good base but didn't do much for my shape. I really changed my shape last year when I did two things; lose the fat, change up my routine.

The routine I do consists of weight lifting first and cardio second, but I still do cardio (mainly running). I change up everything all the time. My running is sometimes long easy runs, sometimes HIIT, sometimes shorter medium pace runs. My weight routine changes each day, each week, Circuits, Intermittent Super Sets, Fibonacci Pyramids, X-sets, Progress Venus Pyramids, and some splits, constantly changing it up, everything a variety of Strength, Hypertrophy, and Endurance.

Legs; In addition to Deadlift's, Stiff Leg Dead Lifts, Sumo Dead Lifts and Squats I do Bulgarian Split Squats, Lunges, Reverse lunges, Curtsey lunges, Step Ups, Crossover Bench Step Ups, One legged Deadlifts (T-Bend), Lunge Matrix, Bowler Squat, One Legged Get Ups, Bower Squat and Calf Raise, Bowler Squat + Stiff Leg Deadlift, Curtsey Lunge + Dumbbell Squat, T-Bend + Y-Squat, Reverse Lunge & Step Up, Curtsey Lunge + Step Up, Y-squat, Narrow Stance Squat

For upper body I do Standing Shoulder Press, Standing Dumbell Curls, Lying Tricep extension, Pullovers, Bent Barbell Row, Standing lateral Raise, Standing front Raise, Curl and Press, Shoulder Press + Curl, Dips, Lying Tricep Extensions + Flyes, Venus Raise (a type of snatch), Bent Row + Standing Lateral Raise, Pullovers, Pushup + Dips, Standing Dumbbell curls + Overhead Tricep Extension, Bent Lateral Raise + Pullovers, One Arm Dumbbell row, Flyes + Pushups, Seated Curl & Tate Press, Seated Curls + Overhead Tricep Extension, Pushups, Pullovers + Dips, Bent Barbell Row, Lateral Raise + Full Front Raise, Venus Raise + Dips, Standing Dumbbell curls + Lying Tricep Extension, Upright Row + Dips, Bent Barbell Row, Flat bench Press, Incline Bench Press, Bent Row Narrow, Bent Row + Kickback,

Then some upper and lower combos; Squat and Front Raise, Step Up & Press, Step Up + Standing Shoulder Press, Squat & Press, Squat & Swing, Curtsy Lunge + Standing Shoulder Pres, T-Bend & Row, Pike Front Rais + Curtsey Lunge, Flat Bench Press + Step Up.

Core: Bar Bell Rollouts (you can start out with Stability Ball Roll Outs), Swiss Ball Pikes (you can start out with Stability Ball Curl Ups), and planks. As you advance Swiss Ball Pike and pushup.

I probably forgot some but you get the idea.

Last June after I'd lost 40 lbs and having lifted for over 30 years (all 10 reps heavy):


After losing another 17 lbs and changing it up all the time. Light, heavy, pyramids, super sets, combos, etc.