All things being equal, disc performance is equal to to negligably better than rim for most dry situations. In the wet, disc is better, hands down. One caveat is what mix of components you have. I've had a real garbage disc/caliper combination once and it put me on the wrong path for a long time. Eventually I had one too many close calls and got a case of upgradeitis. Right now I have TRP Spyre SLC's or Avid BB7's and 180mm rotors on all my disc equipped bikes. I weigh 200, & ride near steep hills, in traffic and this combination is more than adequate my my needs.
In terms of cost: Disc brake pads are cheap. Rotors are expensive. Rim brake pads are nearly cheap, rims & wheel build are expensive. My gut feeling says disc if cheaper if you extend the ownership timeline long enough. I have several worn rim brake rims hanging in the garage. A few winters is all they ever managed.
Last edited by base2; 12-21-18 at 09:42 AM.