SOHC is generally smoother and quieter in operation, and DOHC helps for high revving engines. So the only potential power loss would be from if they wanted a higher redline to make more power.

5th generation

DX, LX = SOHC no-TEC
EX = SOHC VTEC
V-6: SOHC no-TEC


6th generation:

DX: no-TEC SOHC
LX, EX: SOHC VTEC
V-6: SOHC VTEC

7th generation:

DX, LX, EX: DOHC i-VTEC
V-6: SOHC VTEC