Heavier weight does not mean a better chip.
Chips in the casinos are about 10 grams.
Most low quality plastic-with-a-metal-slug-in-them-chips are between 11.5 and 14 grams.
Poker Chips-ChipTalk.net has tons of info on what to buy. I highly recommend them.
What are you going to use the chips for?
Personally I think low quality chips are *never* a good buy.
I hate low quality chips.
I used to have 8 sets of garbage chips that I gave away ... (for some reason I kept winning them in tournaments as a booby prize.)