Two abstracts accepted for oral and poster presentation, but I prefer they are swapped A conference has accepted my two abstracts in the same track, the first for an oral presentation and the second as a poster.

However, I expected the second one would be accepted for oral presentation, as I believe it is more important and relevant to the area and probably to the track and the conference in general. It is also about my primary work, which is more sophisticated and robust than the first one, and I think it would be better for me to present it orally.

But I understand the conference committee have their evaluation and criteria for deciding the way of presentation for each abstract.

Shall I just accept this allocation, which is good anyway? Or is it common and accepted to request, with justification, that they swap the two abstracts - provided they didn't print and disseminate the program yet?
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.