Is prk preferred over lasik?

Depends. The outcomes at 3 months and beyond are essentially equivalent between the two. Prk is used over lasik in a number of situations, such as risk of contact sports, occupation, thin corneas, irregular steepness on topography, or surgeon/patient preference.
Prk vs lasik. There was a conference where ophthalmologists were first asked which procedure they performed most; 90% said lasik. When asked what they would have if they were to have one, 90% said prk. I tell patients this story. 90% of surgical complications are flap related (lasik). And, #1 postop issue is dry eye (more common w lasik than prk). There is more pain and slow recovery but I would have prk.
Sometimes. Prk is sometimes preferred to lasik especially if thin corneas, higher correction, dry eye, mild corneal irregularity or scars, etc.
PRK LASIK LASEK. Prk is an archaic procedure, in my opinion, I performed my last prk in 1999. It's good as it is always slighly safer than lasik, and can be used safely when lasik cannot be, like in the situations mentioned by tal. Lasek is the more advanced form or prk, with the same slight safety advantage over lasik but without the pain and delayed healing and scarring that can occur in prk.

Related Questions

Why is prk preferred over lasik if you want to become a commercial pilot?

Stress resistance. The long term results of lasik and prk are approximately the same. But prk gives a more solid front of the eye less resistant to pressure changes and trauma. For most civilian activities it makes no difference. The military requires pilots to have prk when needed to prevent any possiblity of problem and this may hold true in some circumstances for civilian flight.
Job requirements. Long term outcomes of prk and lasik are equivalent. Requirements for commercial airline pilots allows prk but not lasik likely due to prior concerns of vision changes at elevation. The requirement is antiquated but has not been updated.
Flaps. Prk may be preferred by some airline companies due to perception of flap complications, or postop halos or dryness but that also can occur with prk. Many commercial pilots have had lasik, and ilasik has even been approved for nasa astronauts. The commercial airline (s) of interest may have specific reasons they can share with you.
Not sure it is. The long term safety and effectiveness of prk and lasik are very similar. Classical thinking was that prk may be better in the event of pressure changes since there is no flap. However, lasik has even been studies and approved for both nasa and military pilots.