Let's see, I would have an easier time finding work, I wouldn't constantly feel the anxiety of hiding who I am in public, clothes would (possibly) fit more naturally (instead of a tiny waist and broad shoulders making it difficult), relationships would be more straightforward for whoever I was involved with, I wouldn't have to worry about medical bills as much, I wouldn't need to worry about public restrooms or be as concerned with my safety in public, and I could have children.
Of course I would rather be cis. As much as I appreciate the support I've received, I don't care to be the trans friend in a group of girls and I don't care for the droves of old friends who have come to support me. I didn't transition because I wanted the attention, I did it because I hated my body.
And frankly, I don't get how any transwoman can answer this and say they'd rather be trans. The question never has any qualifiers like "Cis, but ugly" or "Cis, but a completely different person", it just asks if you'd rather be cis. So if everything remains the same except that ONE difference, why wouldn't you want to be cis?