What's the difference between Google Maps with the satellite view and Google Earth?

Which is better to use for pre-scouting?

Also does Google Earth cost to use?

I use the free Google Earth on the home PC when I'm " scouting".  I can measure, draw and mark spots on it.
I use Google maps on my phone when I need a quick view of we're I am when I'm actually in the field.

I installed Backcountry Navigator and never looked back.

Try bing maps, imagy in some area is much better (hi-res), cant do some of the thing google can do though.