I was wondering, out of all 1:16 scale tanks, which ones do better with added weight ?

T34/85 tank needs weight for better traction **BUT ONLY** if you have the gearbox beefed up!

Depends on what you are trying to accomplish, realism or more traction?

The Leo is the best for adding weight as it has the most powerful drive train to pull/carry extra loads without damage to transmission.

Not exactly. I had my Leo 2 and my stug go up the same hill Leo stock, stug 4 with tamiya tiger gear boxes. The Leo made it up the hill about half way. The stug clambered all the way to the top. They both weigh in about the same too. The Leo has less traction in certain terrains.

I was just commenting on the weight management, but true loose material will be forded better with the high profile cleats of the Stug than the Leo.

The Leo has superior traction in wet or rock. The KT probably the best for climbing since the high cleat and wide track.