The north side of the loch is a lovely walk on a more rugged path to start (it becomes well made and maintained further along) with what can at times be an exciting river to cross, Allt Coulavie. I've walked it many times. I've also walked the southern track many times and enjoyed it. You might find that, on the day, the weather, the company you have, your mood, all sorts of things might sway you at the decision point which way you go.