Which of feluoxetine or citalopram has positive effects on memory alongside its antidepressant effects?

Neither: Neither Fluoxetine nor Citalopram actually improves memory. But depression can impact motivation, so that your attention to detail and your will to "try" decrease. This ends up affecting memory, if you're so depressed you don't even care about information that's coming in. By treating depression, these medications may allow your normal functioning to proceed.