I use a depth raider and it does require a coated cable. I works well but the guys I fish with beat up my cable so I've been through a couple (cables) in the past few years. The depth raider is a fine temp/speed probe which alot of guys run, but it does use the coated cable, some guys get many seasons out of a cable, I unfortunately do not. The unit runs $430+ with everything you need. The other mentioned units are at least $100 more if you shop around. Replacement cables for the depth raider run around $50. Uses the same cable as the sub troll unit. Another downside of the coated cable is you can only run the unit on that rigger which also has the antenna. If your cable or antenna goes bad you can't just move the probe to another rigger and keep fishing. Also creates problem for auto stop, at least with my big jon riggers, the hole in the antenna is too small for the autostop bead. Other units mentioned don't have those issues.
Adk1, I use my probe for speed at the lure ALL the time. Temp is important, but many times the current/wind will be so bad you can never get the speed right if you only go by gps or ff speed. IMO speed at the lure is as/or more important than the down temp. I think the unit you're refering to is the fish hawk td which gives you temp at 5ft intervals. Good info to have, but IMO down speed is more important.
Hope this helps.