Acid-base chemistry - determining stability [closed]

I am learning about acid-base reactions and how to identify whether an acid is strong or not by looking at the conjugate base. The more stable a conjugate base the stronger the acid.

However, two of the factors that determine conjugate base stability seems contradictory to me.

1. I understand the bigger the atom, the more stable the base so $\ce{HI}$ is more stable than $\ce{HF}$.
2. The smaller the orbital the more stable the base. So $\ce{sp}$ is more stable than $\ce{sp^3}$.

Now why is a bigger atom more stable than a smaller one, but a smaller orbital more stable than a bigger orbital?