Well technically Reelya sexual reproduction is a lot more inefficient and a lot more prone to mistakes then asexual reproduction.
Much more often are you going to create inferior candidates for reproduction from what were stellar ones.
This is evidently false simply from the large number of counterexamples in existence. I.e. ff that were true, then why did anything ever evolve to stop being asexual? It's one thing to say "Oh well, XYZ might be more adaptive, but we just didn't happen to end up with it." But it's quite another to claim "We already HAD the better thing, and then stopped doing it, on a massive scale" That should pretty much never happen in evolution.
Sexual reproduction has a large number of different mechanisms in place to protect the proliferation of the stellar genes if/when they are found. For example, alpha males fighting each other and the winner being the stud for an entire community of individuals in species like elephant seals.
And as mentioned above, sexual attraction does this as well. Which may sometimes overlap but not always with fighting methods.
Another point to keep in mind is that there IS no such thing as an always and objectively "best" set of genes. You might think "oh that's a really good specimen. ALL of them should be like that" and for the time being, maybe it is the best. But then 10 years later, some new disease pops up, that your "best" specimen turns out to be really weak against, and BAM. All your d00ds are dead all at once. Game over.
(^This is the most glaring and dangerous aspect of big business GMO crops, for example. Not potential danger to your body, but susceptibility to new blights that can wipe out half a country's homogenous food crops. They're extremely fragile compared to natural variety, and several exploited African nations are finding out how true this is already)
Whereas the mix and mash and minced up gene pools of a sexual species may not have full proliferation of the best of the best at all times, but they will be BIASED heavily toward better genes (due to the sexual attraction etc.) and the remaining variability of the rest of them also protects the species by acting as a "gene bank" that provides for unknown future contingencies.