Martyb, I agree that agents representing buyers will frequently steer clients to houses that offer the buyer's agent higher commissions.
However, I disagree with your reference to the 4%/6% bit.
The seller and the seller's agent can agree to whatever commission they want - whether the seller's agent gets $995, or 1%/2%/3%/whatever - irrespective of whatever commission the buyer's agent is offered.
Now, it may be common for the seller to agree to a certain percentage to be split by the sellers/buyers agents, but the buyer's agent isn't impacted by the commission that the seller's agent is receiving.
If I'm selling a house and agree to the $995 plus 1% commission for my agent, I can offer a buyer's agent 3%, and they couldn't care less that my agent is getting 1%.