O-Soto-Gari. It’s different if you have perfect circumstances with momentum and positioning to effortlessly perform a hip throw or different sweep, but all else being equal, I’d say O-Soto-Gari.
O-Soto-Gari (“Large Outer Reaping”) gives you maximum leverage and allows an easy synergy between upper and lower body, coordinating all your strength without requiring perfect timing, a vulnerable position, or the gift of momentum. It’s a quick, simple move that’s easier to pull off on a heavy opponent than a hip throw that requires lifting them or one of the other sweeps more dependent on timing, extreme mainipulation or an already off-balanced opponent.
There’s not much complexity or finesse to it. O-Soto-Gari just takes a little bit of force applied in sync; the push and pull of the arm, the rotation of the hips, and the placement of the leg. When demonstrated there’s not much mystery to its mechanics, its simplicity is intuitive. Yes, there are common pitfalls, but they’re easier to avoid than fancier moves. It’s the first throw I ever learned and the first throw I always teach. And for good reason. It’s easy to learn and easy to do. Within one training session I can always get a novice student to flawlessly execute it. You really can’t say the same about O-Goshi, Ippon Seoi Nage, Tai-Otoshi, Ouchi Gari, etc.
Now, a disclaimer. I’m not saying this takedown will consistently work on a heavier opponent who knows what they’re doing. It’s easy to counter if you’re familiar with the move–the set up for it makes you essentially a mirror image of your opponent who can just as easily do it to you if they know what they’re doing and are bigger than you as the question asks.
However, I don’t train for tournaments. I train for reality. In a self-defense situation, you will more often than not face a bigger, heavier, stronger opponent, and this works fine in that situation if you’ve “loosened them up” first. Contrast that with any hip throw or more complicated leg sweep where more things have to go just right to pull it off. Even if a really big attacker has been softened up, lifting them up is more difficult than simply “tripping” them. O-Soto-Gari is simple and effective.