The difference between these NICs are really negligible. Killer has a great software though, but you need to configure it to make it work right. But yes MSI z87-g45 has better sound than Asus z87-plus.
Component quality is somewhat similar. Both boards are using 4 real power phase with a doubler. So same complexity here. Enough for mild overclocking... Mosfet quality and capacitors are pretty much same again. But MSI using higher quality 60A inductors in its every price range. Asus is only using 60A inductors on ROG series boards.
So at this price range I'd go either MSI or Gigabyte.