Senior,
You probably already know, but just to be sure, the Infinium is a PI machine so it's a different animal than the CZ-21 or Excal. There is crude, if any, discrimination on the Infinium, but it does go deep.
Comparing the Excal and the CZ ( which are both VLF machines by nature), the CZ has to be manually ground balanced while the Excal does not. The Excal has automatic ground balancing/tracking.
The CZ has 3 tones, the Excal a multitude of tones, but they can be distinguished pretty well. The Excal nulls on iron in discriminate mode ( meaning it does not make a sound, ie, it cuts off the threshold ) while the CZ can make a low tone sound over iron in discriminate mode when set to 0. When the CZ is set to a discrim level of 1 or more, the low iron tone is not heard.
The CZ has a VCO, pin point button that when depressed, changes the machine to all metal and you can detune the target. The Excal has an all metal mode but does not have a pin point button. If you want to pin point with the Excal, you have to turn the knob to pin point, which brings it into an all metal mode. But, it is very easy to pin point in discriminate mode with an Excal.
The CZ uses a concentric coil, the Excal a DD coil. I am not sure if you know the difference, but the concentric puts out more of a cone shaped signal, where the DD puts out a signal kinda like the shape of a long, narrow rectangle. Picture that rectangle moving like a windshield wiper blade when sweeping the coil.
The CZ in discriminate mode is a silent search detector, where the Excal in discrim is a threshold based detector.
Both are heavy, but the stock shaft of the Excal is really bad on the arm...most end up getting an after market straight shaft for it. The CZ comes with a pistol grip straight shaft, but a lot of hunters end up hip or chest mounting them due to the 4 9V batteries it takes and how heavy it becomes. In the water, both machines are obviously lighter.
As far as depth, sensitivity to gold, etc...not 100% sure as to which one is better. A lot depends on the user. There are hunters who hit targets at 14-16 inches on the Excal, and the same can probably be said with the CZ too.
If you want another VLF machine to put in the mix, add the Whites Beach Hunter ID 300 ( which is another cool machine). That model can actually visually ID targets in all metal mode with it's lights, where the Excal and CZ cannot ( Not visually. There are hunters who know their Excals and CZs and their language in all metal that can hear what that target sounds like and can size it based on sound to get an idea if it's junk or a good/round target, but those machines don't have visual displays ). However, as the targets get deeper, the ID lights are not as accurate on the BHID.
The Infinium should be put in with the other water proof pulse machines out there when comparing....and its one of only a few, if any, that is a water proof PI that has ground balancing.
I had an Excal 1000...great unit, just too heavy for me ( which again is user preference...I really liked the machine a lot, just could not swing it, even on a straight shaft or hip mounted. I think due to it being an older model ( the Excal II is lighter) the coil was heavy and it seemed to put a lot of strain on my elbow and shoulder). I have a Beach Hunter ID 300 now...it's easier to swing. I never had a CZ-20 or CZ-21, but have and always will have my CZ6a ( which is basically the same as a CZ21 but not waterproof with a few added things like visual display since it's a land unit for the most part). I use the 10.5 inch coil on my 6a and it is a great beach unit.
One last thing...the CZ and Excal are slower sweep detectors...the BHID300 can be swept a little faster. It can cover a little more ground on the wet sand. You really can't sweep too fast when in the water though, so when in the water, its a moot point
Sorry for being long winded, but my best advice is to try and see if you can use a few different machines. Also, put down all the main features you want down on paper and see which detector meets them to it's best ability.
A lot of hunters like threshold based machines, other like silent search. Warranty is always a big thing too as well as reliability.
In addition, where you will be hunting is crucial. Since you mentioned the CZ, Excal and Infinium, I am assuming you are hunting in salt water. If you are hunting in fresh water, first off, a PI would drive you crazy as a first water machine. If it's freshwater hunting, then you have to put other machines in the mix because there are a few other excellent fresh water machines.
JC
