I have the manual 4 gallon and use it most of the time. The driveway is over 1/4 mile and I have to fill it several times and only one water source near the house, so much more efficient with the larger capacity.
I use commercial weed and brush killer so always go back to the garage to mix it.
The battery powered is great and last about four hours and recharges in 20 minutes or about the time it takes to eat lunch.