You don't 'need' to go with lower compression for boost. You need to go with lower compression if you want to run crappy gas...lol
Higher compression requires higher octane, that is all. What gas you want to be limited to is what dictates your compression.
Now, as to your exact question - ALL forms of boost raises compression - doesn't matter if it's from nitrous, a turbo, or blower. The more boost you throw around, the higher your compression rate will be and the higher octane you will require. As Dex said, it's all relative to how much juice you want to throw at it.
But yea, generally nitrous likes the higher compression to start with. If I was building a nitrous car, I personally would have built a 12:1 (or even 13:1)
But I would not be putting pump gas in it either...lol
