Is there a compelling reason for me to move from 2 to 3? I'm not a high traffic site so I'm not moving to a new Pi. What are the configuration settings that you don't have access to if you do the inplace upgrade?
A better decoder if using an RTL-SDR or FA style dongle.
Simple/easy support for Mode S Beast and Radarcape
NEXRAD weather radar
Colour coded altitude
Ability to sort list by distance, country, RSSI etc
Additional aircraft icons
Click to centre highlight aircraft on map
Updated MLAT client
Several hundred bug fixes
Your antenna doesn't seem to be very high so it may not be worth an upgrade. (I get the same range from my basement window test units)
The code should run on your current device, assuming the CPU is not currently high.