[visanj]

I have 2012 Macbook air and recently I tried to compare Macbook air's sound quality with Clip+ and I could not find much difference
 
Is 2012 Macbook air's sound quality equal to iPhone 4s? Anybody get a chance to compare sound quality?

 

[Synthax]

Bump

 

[utdeep]

I have an iPhone 4S right now and I think it has a really good headphone out.  While I currently own an Macbook Retina, I used to have the Macbook Air 13" 2011 model and I don't think it was as good - high noise floor and a lack of detail.
 
Noticing the differences really depends on what kind of headphones you have.  I don't think you'll notice the difference with the Porta Pros (although I love those headphones) but you should if you use your HD-650 or the T70 assuming they can be driven to similar volume levels. 
 
If you don't notice a difference, consider yourself very lucky.  Enjoying the music is much more important than worrying if your source is "good" enough.