JK47's 300 gallon acrylic felt as heavy as my 125 glass. You have factors like thickness that also come into play. Are you worried about moving it or the weight on your floors? Because it's really the water that weighs a lot... A bit over 8 pounds a gallon. So for 100 gallons you're already at over 800 pounds of water without factoring in the stand, substrate, decor, etc.
I worry about the floor. I know the water is the main weight but if the tank it's self weighs less it would help... I might just reinforce the floor to be sure.
when you get into tanks that big, I don't think the difference in weight will make a difference. if your floor can handle 1000 lbs. I don't think 100 lbs. more or less will be a problem.