The first battery supplies more watts at slightly higher nominal voltage compared to the second. The voltage on both (indeed, on any 14V Liion battery) will fluctuate from 16.5V+ down to below 13V.
If you're still looking at brands, you should check out global media pro. They have a 65w np1 for $100. The quality is as good if not better than IDX and most other brands. The only weird part is they only take payment via wire transfer, so figure $30 on top plus another $100 or so for insured DHL 3-day delivery (only option they offer. Considering they arrive from china, the service is pretty good!) They also seem to be the only manufacturer who ships directly from the factory, so in theory their batteries should have the longest service life. I have 4 of their NP-1s, and will happily shell out for more when I need them.
DL