Head swap lang ba? Should be some gains, but I don't know if you'll get the full performance of either the D15B or the PH16... that would depend entirely on whether the compression ratio of the D15B and the regualr D15 in your car are the same.

Con... you're not sure that this will make that much more power... and the condition of the head you're swapping on (is it straight? is the valvetrain still good?) is an unknown... but most mechanics will give a warranty on the job and the head...

Pro... it will make more power, it's a relatively painless job.