Manufactured Vs Natural Strength

I am about 160 lbs. For fitness, I practice martial arts (karate, boxing, kickboxing, judo, grappling etc.). Most of these are with training partners and includes a lot of sparring. So, I am working against the resistance of these partners. On top of this there's supplemental training (bag work, skipping rope, pads, etc.). Now let's say you are 180 and drop down to 160 or if your are 150 and bulk up to 160, what are your chances of beating me? Will you have an advantage because you came up or down in weight? I say no. Reason being, is that my body will function more efficiently at it's natural weight. Now we always here the old saying that all else being equal, the stronger athlete wins. But, that's usually never the case. For the most part, the athlete who is good at what they do usually wins.