1. What is the difference between the two other than timings and bandwidth?
2. which is newer? better?
3. what is the better for my mobo?
4. what is the difference between 1.5v ram and 1.65v ram?
5. can i use 1.5v ram with 1.65v supporting mobo?
Tighter timings, lower voltage and $10 cheaper.
Speeds over 1600Mhz are only useful if you go past 200Mhz FSB when overclocking.
If you do decide to do that, you can easily overclock the PI series by dropping it to CL8.