I just graduated from a local welding school and the technique taught there was the triangle motion. It definitely got excellent penetration and left a very nice weld. We were using the millermatic 252 running 18 and 200. Same 75-25 gas mix. I've tried the other techniques and definitely liked the triangle best for uphill mig. I also tried a side to side weave stepping up slightly with each weave. It worked good as well.
Return to mig welding techniques.