  In this paper we are dealing with two classes of mean curvature type problems
that generalize the translating soliton problem. A first result proves that the
solutions to these problems have unique interior critical points. Using this
uniqueness result, we next derive a priori $C^0$ and $C^1$ estimates for the
solutions to these problems, by means of some minimum principles for
appropriate $P$-functions, in the sense of L.E. Payne.
