The CZ5 will work better on the salt beaches due to the dual frequency and salt mode. I have a CZ6a and it's a great beach machine as well as probably one of the best all around detectors ever. The CZ5 is the same thing except it is not water resistant and has a speaker.
Not sure about the depth comparison between the 2 with the 5 inch coil, but my CZ6a gets coins and rings deep with the small coil and sniffs through the trash easy. You can also bump up the sensitivity using the smaller coil...just sweep slower. It is a great trashy park coil.
I have read that the Edge may be better in iron laden areas due to the CZ's penchant for iron, but here's a tip. When hunting in iron laden areas, keep the discrimination at 0 so you can HEAR the iron. Lots of times when hunters discriminate iron out on a CZ, using discrim at 1 or higher, the iron hit bleeds through but since the low tone is cut off, it will ring high tone and the hunter thinks it's a coin. If there is so much iron you can't stand hearing the low tone, hunt in 1, but when you get a high tone hit, switch to 0 to make sure the low tone is not banging as well. Plus, dig all deep high tone or high tone/mid tone repeatable signals regardless if there is an intermittent low tone mixed in. Lots of times this is a deep, non-iron target. Just sweep slower when checking and if possible, slowly raise the sensitivity. Also, if you read any tips on the CZ's from the forums or the CZ page. you can learn that lots of times iron pin points in different spots when detuning. I think the VCO pin point on the CZ is a great feature since you can size up the target. Most coins, rings and round objects ( washers, caps, etc.) pin point in a very small 'window' when detuning where nails ( especially elongated),wire, bobbie pins, etc. pin point long and in a bigger 'window'
One last thing...if you do get the CZ5, DON"T use a sensitivity level above 3 awhile ( you will still get very good depth)...at least 10-20 hours. This way you will get to learn the detector and not get fooled by some false tones or the deep rusty nails that you think are coins. The CZ's are sensitive machines, and running them hot without learning them first will make you crazy. I know...learned that first hand back in the early 90's !!!!
I would get the CZ5 over the Edge. Just my opinion.
JC
