First, not all the Envy's specs are better. The MBP's screen blows the Envy's out of the water (it's 15.4" at 1680x1050). The MBP has nearly twice the battery life of the Envy. The MBP is significantly lighter and thinner, despite the bigger screen. The MBP has a multi-touch glass trackpad, while the Envy just has the same basic trackpad most laptops have had for 10 years.
But it is true that the Envy has more processor cores, more stock RAM, and a much better video card (which will matter only if you play 3D games).
You have to decide which specs are most important in your daily usage, and whether OS X is worth a premium to you.