Answer:
The beneficial allele will rise faster if it is dominant
Step-by-step explanation:
A dominant allele is expressed even if there is only one (heterozygous) allele present in an individual, whereas a recessive allele requires 2 copies (homozygous). If the allele confers fitness, it is much more likely to be acted on by natural selection if the allele is dominant, as the carrier will actually possess the associated phenotype.
For a recessive allele to be confer fitness, an individual would need to be homozygous. Even if two individuals both heterozygous for this rare allele had children, those children would have only a 1:4 chance of being homozygous, meaning its beneficial effects would rarely be seen and it would take much longer to rise in frequency.