Hi. We decided to use an agency because we wanted a semi-open donor and a fresh cycle. We also wanted more control over selection, screening and testing than we though we could get through an in-house program. A reputable clinic with an in-house pool has presumably screened its donors thoroughly, but we thought it was also in their interest to deem their donors OK. We just wanted an independent relationship with all of the parties: agency, clinic, donor and attorney.
This was, without a doubt, the most expensive way to go. The entire process cost us about $32k. We chose out clinic and agency very carefully. Our doctor rejected several donors we presented to him and we had to not get our hearts set on any particular donor. We ended up finding our perfect donor - she had passed all clinical tests and she had the personal and physical attirubutes we were looking for. But we had to let our doctor do his job and apply stringent screening criteria.
We chose not to work with a frozen egg bank because we wanted an open donor. Same went for some clinics that offered fresh cycles through their in-house donors - we found that most were anonymous programs.
We chose our agency carefully, turning down any agencies that demanded huge deposits or refused to turn over any clinical information about the donor until we coughed up cash. We ultimately worked with Giving Hope, and I cannot say enough nice things about them.
I hope this helps! Best of luck to you!