with a full lifetime warranty is the CZ-3D, unless you can find an old stock CZ5 or CZ70 Pro.
Yes, they work well when hunting slow. In fact, that's the preferred speed with the CZ's.
Which one should you get? The CZ5 is an excellent machine, as is the CZ70 Pro. I prefer the CZ-3D myself. Now before we hear about the 1950 sites, wider target segments and more trash items reading good, let's looks at it a little closer.
The CZ-3D does have the new fourth tone for foil. The great thing about that is that a lot of small gold jewelry falls into the foil range. If you are jewelry hunting, you can specifically listen for that tone without having to constantly look at the meter.
The target segments weren't made wider, as some think, but were enhanced to accept many good targets that were falling into lower target ranges. I might suggest you read Thomas Dankowski's write-up on the CZ-3D with the following link:
http://www.fisherlab.com/fisherbeta/intel/fishintel.pdf
Yes, the CZ-3D was designed primarily for finding older, deeper, coins from earlier sites. The best sites for using the new, enhanced, mode date from 1950, and earlier, however you still can hunt newer sites, and those older sites that are still in use, by using the Salt mode. The CZ-3D will then act the exact same as the CZ5 does when it is in Salt mode with the exception of having a new, fourth, tone. Some will say you will loose depth. That is true only to the extent of very small gold items, and women's thin gold bands, although the loss is very slight. Coin sized objects will still be found at typical CZ depths.
You can read more hints & tips on using the CZ-3D, along with all of Tom Dankowski's articles at http://www.TheTreasureLeague.com site. Just click on the Hints & Tips page, and follow the various links.
All CZ's, as well as all other metal detectors, require some learning curve. I can assure you that if you take the time to learn them, the CZ's are a formidable opponent for any brand, or model, out there.
Hope this helps,
OldeTymer
TheTreasureLeague.com