Two abstracts accepted for oral and poster presentation, but I prefer they are swapped
It does not hurt to ask. You can send a polite email explaining your reasons and ask if it is still possible to swap the talk with the poster. It is possible that the decision of the conference committee was based only on the number of slots available, and they will not hesitate to swap talks at all. It may be also that their decision, as you described, is based on some evaluation of strengths of the abstract and potential interest to it among the participants. In this case they will simply refuse to do as you ask, but you lose nothing but a bit of time.

The request to swap talks is not quite common, I guess, but also not unaccepted or weird. I would say, it is worth to try.