In this post, I compare the nautical (navigational) charts from the following iOS mobile apps: Navionics Boating app, Garmin ActiveCaptain (using BlueChart g2 charts), 0100100 Merellä and Nautics Sailmate. In addition to those, I have also included oeSENC (vector chart) from o-charts.org and photos of the official TRAFICOM paper charts.
The app screenshots are full screen screenshots from an iPad. The computer screenshots (OpenCPN with oeSENC charts) are taken with the same zoom level (the same chart area visible on the same screen area). Larger images can be found on a separate page which only has the images and can be expanded to any width.
Below is a coastal area in Finland shown on different apps and charts.
Navionics and Garmin has pretty much the same level of basic detail as the source for them is the same (Garmin owns Navionics). However, the user generated content differs. For example in the screenshots above, Navionics has some (user added) seamarks that are not shown on Garmin. Sailmate basically shows the raster version of the official marine chart. 0100100 has their own distinctive simplified design.
Below is a zoomed out view from the same area. As you can see, 0100100.fi loses all the rocks when zoomed out. This is probably done to declutter the view, but it is also very dangerous.
There are areas in official charts that have much less detail than charts from, for example, Navionics or Garmin. See below a comparison. As you can see, the official charts are missing a lot depth information as well as some rocks.