Ford Repair: code scanners, snap on mt2500, actron cp9145

Question
I have a 94 ranger with the 3.0 V6, standard trans and air conditioning.  ^The engine will not hold a steady idle. It jumps from around 500 rpms up to about 1500 rpms.  It will finally settle down to a steady idle but only after several minutes of up and down.  It does it when the engine is warm or cold.  I just installed new plugs and wires but it didn't help the problem at all.  It did cure a missfire under load though.  The pickup has 165000 miles on it and the only problem up to now was the clutch which I just replaced.  
Would a code scanner be of help to me in diagnosing this problem as well as other problems?  I am thinking of getting either a auto xray 2000 or a actron cp9145.  I also have a 94 lexus which is obd II and both of these models will do both OBD I and II.  What is your opinion on these scanners?

Thanks for any help.

RYoung

Answer
Hello and thanks for the question...I'll try to help.
 If you are seriously looking in to getting a scanner, I would suggest the Snap-on MT2500. It is the BEST scanner out on the market, also one of the most expensive. But, you do get what you pay for.
I have no dealings with the 2 scanners that you mentioned.
Hope this helps,
Erik