Should i go with f/1.8 or f/2.8 for Star Photography?

Is there a significant difference, enough between a f/1.8 lens and a f/2.8 lens for star photography?
Will the f/1.8 lens let more light in to the point where its very noticeable, and per say WORTH getting over the f/2.8. Or are they pretty much the same that you will not see any differences.

Nikon 40mm f/2.8 MICRO (i love the macro feature)
Nikon 35mm f/1.8

This lens is specifically for taking night/star photography. So if the f/1.8 is significantly better, please let me know. I'm short on cash, and i'm unable to have both lenses to compare them side by side with different photos.

You are getting a 1.5 stops of light more with the 1.8 over the 2.8.So if you want to shoot a long exposure, you will get more light in with the faster lens. This can be helpful, but the question of worth comes at a price. Can you afford the step up? And if you like the macro, then you are losing one thing to get something else.

But keep this in mind, if you are really interested in astrophotography, then you can always stack your images. You shoot a lot of relatively short exposure shots and then use software to combine them. You reduce the intrusion of noise (which will be higher with the 2.8 because you need higher ISO for the same exposure).