Hello RH of Silver Spring, and welcome to the boards!
On the advice of RS most people here opt for Varenna which has both a train station, a ferry station and small town charm. The mid-lake ferry that stops in Varenna services the larger upscale town of Bellagio and the fading resort town of Menaggio. From Bellagio you can connect to further ferries if you want to.
I can't advise on Lecco - it is certainly a larger town than Varenna but unless you intend to stay only there I would check the ferry schedule to see what other towns you have access to that way. I don't believe the Argegno side of the lake has any train service so that would require something like training to Como and ferry or bus to Argegno.
For the two nights you're up in the air on what experience are you looking for? A big city, small town, museums, cafe culture lifestyle, shopping, Roman ruins, gondolas on canals? All of these things are within reach of Milan but knowing what you're looking for will help narrow the search. Classic Italian tourist towns like Florence is 2 hours and Venice is 2.5 hours away by fast train. But it all depends on what you want.
Hope that helps,
=Tod