Re Suitable hall effect sensor
New to electronics - understand the basics!

I have seen mention of this Hall Sensor in the thread:-
"Also I want to use the H501 Hall switch (Unipolar type) from www.Conrad.de with the ordering code 185120-62"


Is this essential?
I have found this hall sensor-
http://www.jaycar.com.au/productView.asp?ID=ZD1902
__________________________________________________ _________________
UGN3503U Hall Effect Sensor

A miniature sensor to accurately track extremely small changes in magnetic flux density - changes generally too small to operate hall effect switches.

Specifications:
- Operating voltage: 4.5 - 6V DC
- Supply current: Typ. 9mA
- Output voltage: Typ. 2.5V DC
- Output resistance: 50
- Size: 4.5(W) x 4.5(H) x 1.5(D)mm
Applications include notch sensor, current monitor, gear tooth sensor, etc.
__________________________________________________ __________
Or should I go for the switch type?
http://www.jaycar.com.au/productView.asp?ID=zd1900
__________________________________________________ __
This device consists of a Hall Effect semiconductor sensor separated across a small gap by a magnet. In its normal state the Hall sensor (with inbuilt output transistor) is conducting. It will sink up to 40mA between the impressive temperature range of -40 to +150 degrees C. When an iron vane is introduced into the gap between the Hall element and the magnet, the output transistor switches off. The sensor is hermetically sealed, resistant to petroleum products and incorporates metal bushed mounting hols to facilitate fitting to a carrier plate, bracket etc. It is ideal as the commutator for an electronic ignition; however it has many other usage areas. Lead connections: Red V+, Black earth, Green signal (on/off).
__________________________________________________ _________________

My concern is that from reading about hall there are analogue and logic level hall devices.
What paremeters should I be looking for?
Cheers Jeff