Either strong hand or weak hand reloads are viable. I generally use a weak hand reload for moons, and a strong hand reload for speedloaders, but I can switch if the situation calls for it (e.g. cramped quarters).
There are advantages in being able to switch hit, but I'd start off with the one that comes more naturally.
One note on the strong hand reload, though: Watch your muzzle! Ideally, you'd get the muzzle vertical to help clear the empties, but this can put you perilously close to a muzzle violation, and a possible DQ if you mess up. I try to keep the muzzle a little a little forward to be safe (see pic).
BTW, as you can see in the photo, my strong hand immediately goes to the speedloader as soon as
The Switch is made. When the gun comes down, the speedloader's waiting for it, and the rounds go in. Lowering your 2 hands (& the gun) before grabbing the speedloader is very common, but a real time waster.
Another time waster is closing the cylinder. Many pinch the cylinder closed with their fingers, then
raise the gun. Bah. Once the rounds are in, snap your eyes to the target and push the cylinder closed with the butt of your weak hand as
you raise the gun. Your weak hand is perfectly positioned to do this as it's re-establishing its grip.