When you copy/paste files between Google Drive accounts has an importan advantage. If you copy and paste files between Google shared accounts, the files are transfered directly from one account to another without going through your Pc.
You can share your accounts with Air Explorer. Fisrt, open your Google accounts.
Choose the folder you want to share and click left button and in the menu click Share.
Write the Google account email and give permissions to your destination Google account.
Once shared your account, you can refresh and the folder changes the icon. Then, in the destination account, the source folder can be seen as a Google Drive folder.
When the folder is shared, it is shown inside a disk drive in the destination account. Then you can transfer files quickly between it and other of your Google Drive folders without passing through your computer.