My World Book - Mac OS - Slow Transfer Rate

I have been struggling with this for quite some time now. I have a white 1gig My World Book NAS connected to Wireless N router. My only computer is a MacBook Air connected wirelessesly. 

When I transfer files to the device, whether they are small or large the transfer speed is VERY slow. After researching this I was able to determine that the device is known for being very slow. I recently setup the FTP server on the device though and I find the transfer speed signifigantly quicker. This does not make any sense to me. How can transfering the files onto a device be quicker using one method than another? Is there something limiting the file transfer that is not in place for the FTP transfer? 

Also check the link below for some suggestion on how to improve the transfer speed.