Ah, that’s a big price gap! I’d say just go for the original version! The sound is identical!
Tyll at Innerfidelity does good objective measurements of broadband isolation, which is an easy way to compare isolation between different headphones at a glance. And far beyond what I can possibly provide you!
He rates the MSR7 at 15dB of isolation. (You can see the number near the lower right of his chart pages)
The NC model achieves just a couple more decibels across the spectrum, though it has a bigger impact in the lower frequencies.
If you’re not doing a lot of flying or sitting near a droning noise like computers/ an air conditioner/on a train/etc., I think you’ll do perfectly well with the standard model! Most of my review applies to those as well, since they’re nigh-identical outside the noise cancelling.
Hope that helps you out!