What are the real, usable, differences in the three? Plus adds aerial, but is that really that usable on the water? Smartstrike has some nifty search features, but has anyone really used them and do they seem legit? Trying to figure out what mapping cards to go with for my Helix 12 I'm installing.

TIA!!!!

All three have the same contour mapping for the same model year. The version number can be different for the same year.
Plus has satellite imagery for HD locations
SmartStrike has fish location prediction software for HD locations.

If you want to try one lake to see which version to get, just purchase and download one to a regular memory card via Chart Select. You can choose all the features (layers) plus several years of satellite imagery.

I have both the Lakemaster plus and the Smartstrike cards in my graphs.
I use the Smartstrike on one of my Helix 12 at the console to get a feel as to where the bass may be during that time of day if I am at a lake I do not know all that well. I also use it for Navigation as I go about the day on the lake.
My Lakemaster + cards are used along with my SI/DI or 360 graphs just letting me know where I am concerning the contour of the lake.

I run the standard Lakemaster in my Helix 7.............it does all I need it to do