How valuable is being in an A+ rank CS conference with a short paper?
I'm wondering how valuable is to have a short paper in a top conference?!


That depends a bit on what you define as "valuable". As Buffy says, having a presentation and presence at a top conference is certainly very valuable in terms of visibility in the community and opportunity to make connections (never underestimate the importance of those!).

However, in my experience, as a line in your CV, everything that's not a full paper counts for very little, even if it's a short paper at a top conference. In other words, if that is intended to be the main paper of your PhD and you intend to go onto the job market with this work, you need to get it accepted as a full paper. If it's just a side project, or just one in a longer string of papers that together form your PhD, leaving it as a short paper and taking the opportunity to attend the conference and get your name out there may be worth it.

I should also say that, assuming your reviewers are right and all it needs for this work to become excellent is some presentation-level cleanup, it feels like a pity to not do this small additional work and try again at the next deadline for a top venue, rather than downgrading it to a short paper.