It all depends on what the potential/suspected problem is as for what test is best. I've had both. Manometry cannot determine if aspiration is taking place which is the most important factor in swallowing problems (IMO)...fluoriscopic swallow study can tell immediately. It can also tell lots about delayed swallowing and other mechanic problems in that first few motions of the swallow, that the manometry cannot. Manometry is great for suspected motility problems, spasms, reflux, etc...where the fluoriscope is pretty much useless for these. So comes down to what you're looking for.

PH test is good to determine reflux. I don't think they put patients through the trauma of manometry just to determine length of esophagus. I believe they have been doing PH probes long before manometry was even widely used. Don't they just do a couple follow up x-rays for ph probe placement? Been a long time since I had it done, can't remember.