I only recommended the HD668B's because for the money they are a really great pair of headphones and they are head and shoulders above most other things in your price point and even a decent amount above it in terms of soundstage. But if you really cant afford to pay that little bit extra then i would suggest you pick the sound quality over the benefit of a replaceable cable, of course unless you are prone to throwing your headphones, tangling the cord and running it over in your chair. Im not to familiar with the plug on the skull candy headphones but there are cable out there that come with a mic on them so if you need a mic as well and the skull candys support a cable with a built on mic, that may be worth going with over the 429's. Its really up to you and what you want out of your headphones.
for reference, a good place to compare headphones is
http://www.headphone.com/pages/build-a-graph . There are a lot of headphones that arent on this website but they stiff cover a wide range of headphones so depending on your preferences you can pick a pair of headphones for your exact needs.