  We study the complete moduli space of vacua of 3d $\mathcal{N}=4$ $U(N)$ SQCD
theories with $N_f$ fundamentals, building on the algebraic description of the
Coulomb branch, and deduce the low energy physics in any vacuum from the local
geometry of the moduli space. We confirm previous claims for good and ugly SQCD
theories, and show that bad theories flow to the same interacting fixed points
as good theories with additional free twisted hypermultiplets. A Seiberg-like
duality proposed for bad theories with $N \le N_f \le 2N-2$ is ruled out: the
spaces of vacua of the putative dual theories are different. However such bad
theories have a distinguished vacuum, which preserves all the global
symmetries, whose infrared physics is that of the proposed dual. We finally
explain previous results on sphere partition functions and elucidate the
relation between the UV and IR $R$-symmetry in this symmetric vacuum.
