In reply to Martin W:
Not a dentist, but an enthusiastic user of their services:
Firstly - have all three x-Ray's looked at by one of the endodontists - radiographs are a 2d representation of a 3D object and slightly different views can give different information. The dentists should all be happy to share the images with each other. It makes sense to ensure whoever guddles about in your gob has as much info as possible.
The two approaches to examining the root are variations on the same theme - ask the endodontists you like best why they use the procedure they advise rather than the alternate. If possible ( and the data may not exist) ask for success/complication rates of the two techniques in the general population and the individual practitioners hands.
I'd defer bridge vs hole vs implant until the roots been thoroughly looked at again. I'm prejudiced towards implants as both parents have had bridges which have caused a fair bit of grief, but implants are costly as you say. Again though, try to get clear data on cost/success/complications upfront.
HTH