4-1 > 4-2-1
Think about it this way: you're really only using your low/mid power off the line which is so little of your power band. You use the mid/high end power SO much more than the low/mid power because you may be driving on a highway or just cruising down the street. You will get more use out of a 4-1 header, imho.
Also, don't believe all the hype about SS headers. They do rust too. I had a DC 4-1 CC and it rusted after a while. I simply resprayed it with some silver BBQ paint and it looked brand new and didn't rust again.
hih