Isn't 2-piece better?

No, IMO, i think that the one piece is better because u get more flow. ;)

I have a 2-piece DC

DC Sports makes 1-piece and 2-piece headers for both SOHC and VTEC models. Take your pick:
DC Sports Headers (http://www.dcsports.com/pricesheader.htm)

I also agree with 90CRXZCSi. One piece header is better overall due to more airflow than the two-piece.

2 peice is 4-2-1 it gives moderate power gain through out entire powerband. 1 peice 4-1 gives you huge top end gain, but gives up just a lil bit of torque, not a bad thing if you spin tires down low like i do... go with 4-1.