Which acer laptop?

Can't decide on which laptop. ACER ASPIRE AS8410TZ-4982 Time Line or ACER AS4551-2728.

AS8410TZ-4982 is $500 and has:
-Pentium Dual-Core SU4100 1.3GHZ (800 mhz bus, 2mb L2)
-3gb RAM
-250 gb HDD
- Intel Graphics Media Accelerator 4500MHD
- Other misc specs: http://www.thesource.ca/estore/product.aspx?language=en...

AS4551-2728 is $550 and has:
-AMD Athlon II Dual-Core P320 2.1 GHZ (1066 mhz bus, 1mb L2)
-4gb RAM
-320 gb HDD
-ATI Radeon HD 4250
-Other misc specs: http://www.bestbuy.ca/en-CA/product/acer-acer-14-laptop...

Now I know the first will give me long battery life and the second in theory better performance. Is is significantly better? I do like long battery life but 1.3GHz just feels very outdated. I don't plan to play games but do plan to watch HD video, multi-task a lot, etc.

Your input? Again the main thing I am debating here is the CPU in each laptop and whether it's worth it to buy SU4100 CPU for the battery life.