I think Nas discography has been more consistent, even if you compare Life Is Good to MCHG, to me it isn't close, Nas would take that. Nas has mostly kept depth and purity to his music while at times Jay has just gone all out hopping on trends which hurts the quality.
I mentioned Jay to me has 2 classics, Nas to me got around 4. I think Nas has more depth as I mentioned, is more creative and conceptual, better substance, arguably more consistent lyricist, I think his music touches you that bit more. I think he's more poetic, has elements of spirituality in his music more than Jay which gives Nas shyt an extra layer and profoundness at times. I think he's a better storyteller for the most part.
Ultimately I just think he's made better music overall, more timeless ish. I realize this is subjective though and if someone puts Jay ahead it's all good cause he's great too, but Nas to me just been much more consistent over the years than Jay. I listen to LIG and while I don't think it's classic it's a very good album, MCHG was kind of wack to me, and disappointing, to me in most cases Nas has normally been a step ahead of Jay when it comes to albums throughout their career. That's why I personally pick Nas, but Jay is a legend and I am a fan so respect to him too...