I applied to a few programs and they really don't care as much as you have a certification to satisfy CAMTS if they are CAMTS certified. I think they updated their standards to remove the CEN as an accepted cert.
From what I hear CTRN and CFRN are very similar since ASTNA made the test. I took CTRN since I was on the ambulance at the time. However, a lot of people haven't heard of the CTRN since it is newer and not published as much but that will probably change since CAMTS has it in their new standards pdf. They also like the CCRN.