Illmatic is like getting high with a nigga from Queensbridge.
Ready To Die is like getting drunk with a nigga from Brooklyn.
Nahmsayin?
There's more to it, though. Illmatic is about being immersed in the worldview of the artist without being setup to understand it first. You're diving headlong into these themes without preparation and you're not necessarily expected to adapt, either. You just swim through it and if you have a good time, that's great! If you don't enjoy it, that's okay. Come back another time.
Read to Die is presented from start to finish in crystal clear terms that any English-speaking adult can understand. We can attribute this to the fact that BIG was formally educated and Nas was not. That's not a knock on either guy. It's just history. Biggie learned cross-cultural clarity and Nas never did.
Anyway, as far as pitting the authorial emcees against each other goes: AZ has the best verse on Illmatic. Biggie obviously has the best verse on RTD. Take that (take that take that) for what you will.