Confused with different types of proximity sensors

I have come to know that there are three types of proximity sensors namely inductive,capacitive and photoelectric. Now, I am not interested in metallic obstacles so inductive is of no use to me. The question is among capacitive and photoelectric proximity sensors which should I use for which type of obstacles?
Also, among photoelectric there are retro reflection type and diffused reflection type of sensors? How should I choose between them?
I have successfully worked out CDD-40N sensor which is diffused reflection type photoelectric sensor.

You forgot ultrasonic =)

What you're asking is FAR too broad in scope for anyone to answer, you have to present a specific situation that you're trying to solve and then some suggestions might be bad, there are many pros and cons for any type of sensor and none of them will mean anything if we don't know what the application is.

I have a line tracer robot. If the bot encounters a pole in the path then my bot should to pick an object placed on the pole, and put it somewhere else.For detecting the pole and the object on pole(object is cylindrical in shape) I will be using two different proximity sensors. So under this situation which proximity sensor is to be preferred for which application?

You're leaving out too many details. What is the size of the robot, the poll and the object on it, what are they made out of?

Diameter of the pole is 30cm,height is 80cm it is made up of some metal coated wit white paint.the object is of plastic.As I have already told,it is cylindrical in shape.It's diameter is 40cm and height is 25cm. Bot chassi is 60cm by 60cm square and height of my robot is 50cm.

Is the pole always in the middle of the path, and is the ball always in the same start position?

Sceadwian said:

You forgot ultrasonic

Click to expand...

Also, mechanical.

yes the pole will always be in the middle of the path and the bot will always be in the same start position.