1) not really sure what the question is? If the specs are the thing for you, then go for the machine with the best specs. My macbook is plenty fast enough for me.

2) I like the retina display because I can crank my resolution up to 1680x1050 (on a 15") and it looks great. Font rendering on the retina displays is outstanding on apps that support it.

3) I can confirm that the Dell is not an Apple product.

I'd be unhappy if I had to switch from a retina macbook or an Air to the dell, mainly because of the screen. YMMV.