The collecting area of a telescope is roughly proportional to the square of its radius (for a circular aperture). I say roughly because you also have to factor in the small fraction of light blocked by the secondary if we are talking about reflecting telescopes.
In principle the angular resolution decreases as the reciprocal of the radius (that is, the smallest resolvable angle gets smaller). In practice, this may not be the case for ground-based telescopes without adaptive optics capabilities, where the smallest resolvable angle could be determined (for large telescopes at least) by turbulence in the atmosphere (a.k.a. the seeing).