In short to say a 6s setup is better than a 4s for a truggy?

All depends on the components used. A quality motor that is ideal on 4s is still going to be a better setup than a cheap motor on 6s. I dropped my truggy down to 4s this year and things are staying cool.

Problem is 4s needs more Mah n heavier than 6s with less Mah.

I can't say for sure but I would have to think that batteries from the same manufacturer and the same model or series would way about the same for a pack that contains the same amount of energy. Your 6s 3300mah is aprox 73.25 watt hours so looking for an equivalent 4s you would be looking at 4950mah so basically a 5000mah pack. I bet there about the same weight.

I just compared the zippy flightmax 30C batteries. A 3300mah 6s weighs 544g and a 5000mah 4s weighs 527g so that kinda blows your theory that a 6s pack is lighter

Yes my mistake, but I trying a new batt Acorn racing. It's lighter. But must see how's the cost.

Zippy 4s 5000 is one of the heaviest in the market.