Did a search and couldn't find anything. Which GPS puck unit for Helix 10 MSI+ G4N?

There are two of them, one works with Helix unit up to the Solix models and one works Helix through the Apex models. Besides that, I can't find any differences.
So both should work with the Helix units but is one better?

These are the two model numbers of units that I find: 408920-1 (Helix to Apex) vs 408400-1 (Helix to Solix)

I don't foresee me buying an Apex unit anytime soon, so just get the 408400-1 unit?

Humminbird has two currently:
AS GPS HS is the combo GPS and Heading Sensor. It is the only one Humminbird has and is for all their models.
AS GRP is an GPS-only antenna and is the only current model for all their models.

Either of those will connect directly to a Helix via the COMM port.
To use either with a SOLIX/APEX, you need an adapter to connect to the NMEA0183 port. That adapter is AS GPS NMEA for the SOLIX and AS GPS-APEX GPS for the APEX.

In all cases, the external antennas connect directly to the display and are powered by the display.

Thanks so much Wayne. After reading specs for way too long, my brain was just scrambled. Thanks for pointing out that one of the units has the Heading sensor and the other one doesn't.

This video: https://www.youtube.com/watch?v=sUZMTqeovR8 (10:08 time stamp) said that I needed one to be able to mark waypoints while using Mega live in landscape mode. Landscape mode was the only mode on Mega live to mark waypoints. So I went from: "I don't need one" to "have to have".

Thanks again.

I read that the Helix has internal GPS in the head unit. what is the reason for the external Gps puck? is it for the heading function?
also is the Helix 12 CHIRP MEGA GN4 SI+ in case you want to add active target ? or network units?
Im not planning on using active target or networking units so what else does the plus do? I read up to 20 percent better imaging,, anything else,.
i just want a humminbird stand alone unit with great SI, DI, AND 2D with mapping.. and a external, stern mounted transducer. keypad function.
There seems to be a big price difference between the { +] and non { +] units and I dont want to buy functions I wont use.. thanks

For the BEST Waypoint accuracy for those marked when viewed on sonar, the GPS antenna should be near the sonar transducer so position and sonar are at the same place. Also some installations block the satellite signals and the antenna needs more exposure to the sky. Heading stabilizes position when GPS cannot establish direction <.6 mph. Humminbird units turn off the map curser when at less than .6mph so if you need positioning/mapping to function, a Heading Sensor stabilizes the Chart view and keeps the position icon active for direction.
For a console display, the GPS antenna should be at the transom where the sonar transducer is. For a bow installation, the internal GPS antenna does OK. Heading is typically not needed when running the outboard while at the console (can't go slower than .6 mph) so Coarse (GPS calculated direction of travel) works well then, just at the bow when fishing so position is stable.

Active Target is a Lowrance product so no Helix will work with it.

MEGA SI+ and MEGA DI+ units are more powerful than older units or non + models (more SI Range and more DI Depth capability) and are the only ones compatible with MEGA 360. A Helix 12 G3N SI and DI model and Helix 12 G4N SI and DI model are the + models==older ones are not. G4N's are the current model. A SOLIX G2 SI and DI models, and G3 are also + models as well as the APEX.

One more thing, a Helix unit will not subscribe to Heading separate from GPS so putting a AS GPS HS at the transom for a bow unit to have Heading won't work correctly (a boat length's GPS position error). A SOLIX or APEX will subscribe to Heading separate from GPS.

If you have Minnkota iPilot LINK, you can subscribe to its GPS/Heading for a bow unit.

This is four Helix units networked as an extreme test example. Three of them have an External GPS antenna (two with Heading Sensor and one without) connected and there is also iPilot LINK as a GPS source. All four units have the same 8 choices for GPS.