I’ll bet you are just like the rest of us; we like to maximize our catch and don’t think enhancing our efforts with electronics is cheating. Because there is almost always a down current I think down speed is the most useful of all. Exception might be when someone calls on the radio and tells you location, depth, lure, SOG and compass heading. When’s the last time that happened?
I’m on Depth Raider’s prostaff so……. That being said no matter what you buy your catch rate will go up. I run my probe on my shallow rigger because it won’t be in danger of catching the bottom and less blowback. I always run a lure off that rigger if there are enough fishermen. When I set or retrieve the out and down probe rigger I turn the rigger to a 45 angle as this reduces the stress on the coated cable. I run Big Jon’s that have nice big rollers but some other brands have smaller rollers and harder on coated cable. My cable is around 6yr old and still fine.
Good luck with your long term investment.