Pork I just signed on to my Navionics account and yes my account expired so I must pay $14.99 for the update if I desire. 
 
I'm with you when it comes to paying for an APP but I find the Navionics to be worth while.  Heck when I was in Gulf Shores I pulled the APP up on my phone for the local lakes.  The only downfall is using my phone, watching a small screen and keeping the stupid battery charged.
 
I did see the APP has "Bluetooth" capability so it should connect with sonar units having "Bluetooth" and I'm hoping computers/tablets too.
 
I too paid $10.00 for my first APP and no further charges unless I want the update.  I did let my account lapse so I don't know if the update would have been cheaper had I stayed active.
 
Another nice feature with the APP is being able to pull up your favorite lake while sitting in your easy chair (or waiting for one's better half at the hair salon) and plan your next fishing trip.  I find areas I think might be productive (and they usually ain't) mark them and the APP will take me right to them.  Also, I have searched areas on the maps I am familiar with and so far, I have found the maps to be accurate.
 
Features include uploading information for others to see such as obstacles or, laying a trolling route right into the fish habitat getting me snagged. lol  Seriously though, a guy can find all kinds of info provided by other anglers.  Not so sure I believe all those areas marked on Pymie labeled "walleye" though.
 
 

Coljo, Do you think it is the Humminbird unit being more accurate than the Lowrance or the installed charts? If we could ever coordinate our schedules at the lake I would appreciate a peek at those units and their + and -'s.  I do love the boat. Have been using charger but have not had time to set up the trolling motor.

The GPS tracking on my Lowrance was less than expected.  The charts had nothing to do with it.  May try running the figure 8 buoy test again with the newer models on board.  Will have to do it on a lake other than Pymatuning...fishermen racing towards two buoys may be dangerous.

Navionics has an online chartviewer that you can preview lakes to see if they are suitable.
https://webapp.navionics.com/#boating@12&key=_ao%7CFlrhjN
Many of their lakes are poor on detail, but usually show major features (example attached, same hump in both pics).
As far a Pymatuning goes, the Navionics map is good.  The Humminbird LakeMaster map has better detail in key areas.

Coljo,
I have heard from others also that details on the Lakemaster in Pymatuning was better. They said the old roads and bridges are shown on Lakemaster but not on Navionics. Does Navionics show depth adequately? I fish depths ice fishing and have never had a GPS of any sort. I somewhat old schooled it but drilled lots of holes and checked depth with my Vexlar ( not old school). I also fish the humps in other seasons. Do either one show structure brush and man made cribs?
    I would have already bought the Lakemaster however it covers only some of the waters I fish. Navonics seems to cover most. When I get conflicting +'s and -'s, I have a hard time making a decision. Probably purchasing either of them would vastly help me on any lake they cover, being as I have never experienced a GPS lake program of any kind. Sort of like getting a GPS for for a vehicle, after having one you do not know how we functioned without them.

Guys I'm not sure which version or map you would be viewing using the Navionics. But the Nav maps app I use, be they Pymie, Wilhelm, Arthur, ect. do show contour in great detail, as well as roadbeds, bridges, fish habitat, ect. GPS appears to be spot on including the speed.

The only problem I have is using my phone with such a small screen. The old eyes just aint what they use to be. 😒

Thank you to all that responded and have given me insight into this comparison.
    I am now trying to resolve why Lakemaster has no listing for a couple lakes I fish in their lake list. A friend has a lakemaster chart that includes both lakes. If you talk to a Rep. you get only answers directly from their site. I finally got a response from someone who seems concerned. They want to know what model # he has. I hope he can provide it. These reps. obviously do not know their product. Let you all know what I come up with. I want to go with Lakemaster do to its better resolution as Coljo pointed out, however if I can not get the coverage on lakes I fish I will go with navonics. Thanks again.

If your Helix is a G2/3 the Zero Line card may be an option.  I don't have one but will explore that option if I go to an unmapped lake.