I personally like the Adafruit approach, as it can be used with a case. The other one would be difficult to remove without disassembling the case.
If you never need to change, it, I can see the advantages of the other approach.
BTW, I used the Adafruit adapter to fix a broken Pi. The other way wouldn't work, unless you truly never needed to change the card, since it's now glued in!
Here's the writeup:http://baldwisdom.com/repairing-raspberry-pi-sd-holder/