HIS versus Saphyre

First of all, Sapphire. Not Saphyre.
Second of all, the memory bus is measured in bits, not megabytes. (the bus measures how fast the card can use the memory)
Third of all, just because it has more memory does NOT mean it's a better card.

As a matter of fact, the 4670 has a narrower bus than the 3850. The memory is clocked at a bit faster speed, though.
The 4670 may handle Anti Aliasing a little better, but for the most part the cards will perform the same.
The 4670 is not a powerful enough card to handle that much memory anyway. It would have made hardly any difference to get a 512mb version. It's all about the stream processor count, and those two cards have the same number of stream processors.

Hopefully the 4670 has ddr3 ram and not ddr2...

4670 has ddr3
4650 has ddr2

actually its a 4670, i did a benchmarking with 3Dmark, and was surprised to see that my Saphyre HD3850 passed with a higher score than the HD4670. so i need to make an RMA to tigerdirect.ca... man, its gonna cost me something...

4670 and 3850 should be equal on performance, did you install the latest driver?
3850 consumes more power than 4670.
Have you tried comparing them on games?