The real important issue here is that all you need to accomplish is converting SOMETHING from the PC to ttl level SERIAL I/O for the Arduino. So it doesn't really matter... as long as what you give Arduino is what it expects.
I think the important point here is to know how you will use the custom assembly you will make and how much it will cost you.
For example: For breadboard solutions... I already had a Parallax USB to Serial Adapter so I didn't need to mess with my own Surface Mount device... I had something off the shelf. I also have a Schmartboard Serial to TTL adapter...
At first glance, it would look like I spend $20.00 more than I needed to... but the bonus is... I already had these parts for other projects and they just sit in my Breadboard parts collection. I can easily use these parts other AVR or PIC projects.
The FTDI part clearly has "ease of use" handled. It's probably why Parallax also selected this chip for their products.