Are you moving them yourself in your own vehicle? Not the "best", but the cheapest is the U-Haul small boxes (16-3/8" x 12-5/8" x 12-5/8"). I’ve moved multiple times with those and had no issues.
I added bubblewrap and extra cardboard pieces on the ends and top for additional protection.
I’ve also used the Ultra Box plastic corrugated boxes from Bags Unlimited, but those are overpriced and don’t seem to provide much additional support.