What is the best resolution for external monitors (screen extending) on a 15" MacBook Pro (Mid 2014)?

I'm trying to decide between two resolutions: 16:10 ratio (1920x1200) or a 16x9 ratio (2560x1440). I know the native resolution for the MBP has a ratio of 16:10, so it seems like the 1920x1200 resolution monitor would fit that nicely, but the second option has a "higher" resolution at a different aspect ratio. Would the external monitors appear fuzzy next to the MPBs native 2880x1800 resolution when extending a desktop? What is the best type of connection to use between the monitors? HDMI? I know next to nothing about the process of connecting or choosing external monitors, so any information would be greatly appreciated.