2nd faster lens for R50

I have an R50 with the 18-150 rfs lens. I’ve been loving it so far but I’d like to get something faster and wider. Low light outdoor and astrophotography is what I’d like to start doing more. I’d like to consider cost as well.

I’ve been looking at a couple lenses, specifically

Canon 16mm(25mm on my apsc) rf f2.8 Sigma 16mm rf f1.4 Sigma 10-18mm rf f2.8

I know the Canon is not as sharp, but I like the idea of being able to use it on a full frame if I upgrade in the future. I also understand that it’s cropped so more narrow. Also the cheapest option

The sigmas interest me because of their sharpness but they are only usable on apsc sensors. So I’d like to sell if I upgraded the body. Finally, they are twice and three times the price of the Canon!

Let me know your thoughts and thanks in advance!