and I use both, the 5 on land, and the 20 in the water, although I've used the 5 in the water, chest-mounted, and the 20, hipmounted, on land during a rainstorm.
Because of all the iron in the dirt here in MI, I use my CZ-5 in the SALT mode all the time, to help with the dirt. Because of that, I'm not distraught over the 20 being locked in SALT mode, as it helps with the mineralization in the freshwater beaches here.
I don't worry about the lack of a meter on the 20, as I dig anything that gives a mid- and high-tone in the water, and will often dig bouncing low-mid-high tones as well. I don't run the pinpoint while I'm in the water either, so there's no need for a depth reading on targets.
The 20 is heavy. I hipmount mine for all hunting applications at this time. However, in the water, it will float, so if you rod-mount, you don't have the weight, just the mass and water-resistance to worry about.
I have not had to send my 20 in for warranty repair work. I bought mine a few years ago, and was able to get a "demo" unit from a dealer, with the blank warranty card. If you can get a new unit, get it now, as they aren't being produced any more, and the supply of new units with warranties is dwindling.
HH from Allen in MI