Ive been to Lake Como and I stayed in the city of Como. I loved it- the atmosphere, walking through the streets, the lake nearby to do boats or paddle boats, the shops, all of it. Are the bellagio and varenna really that much better? I know they are all different and Rick advises them over the town of como, but am I really missing out if I just go back to como where I know ill like it?
I've visited Como (for the day) and stayed overnight in Varenna. I much preferred Varenna to Como. Now I visited Como in December on a cold, overcast day and Varenna in October in the sunshine so the weather partially influenced by opinion. Varenna has this lovely promenade around the lake and just seemed much prettier than Como. If you have the chance, rent the Rick Steves video that includes Lake Como and you will get some shots of Varenna.
I stayed in the city of Como in May. I stayed at the Hotel Continental which was within walking distance from the train station. The town is pretty, with tree lined hills. I walked in to town and to the ferry and took a 1.5 hour trip to Bellagio for the day. It was beautiful, and I might consider staying for a few days but the boat system isn't as frequent as you would hope for so if you wanted to explore other towns on the lakes you are a bit limited. I remember waiting for the ferry back to Como, and hearing that the fast hydrofoil boat was cancelled because it broke down. Those folks had to take the slow boat.
For me, I definitely want to return to Como, and I will probably explore other towns but still use Como as my base.