personally I would go with pentium 4 650, specially if you want to use it for gaming.
The p4 650 is (3.4Ghz, 2MB L2, 800Mhz FSB)
Pd 805 is (2.66GHz, 1MBx2 L2, 533 Mhz FSB)
The Pd 805 has speed of 2.66Mhz, and just 533MHz bus speed, so it will not perform good in gaming since most games don't support dual core CPU, and even if a game support dual core, I doubt that Pd 805 will be able to beat P4 650.
For video editing and multi tasking the Pd 805 will perform a little better.
Also don't forget that P4 650 support Hyper-Threading which will help to perform better in multi tasking and video editing.
The P4 650 is overall is better than Pd 805