Coming from Switzerland, you should consider the journey as well as the destination.
To get to Stresa, you take the train south from Spiez in the Berner Oberland, likely with a change of trains at Brig. This route passes through two long tunnels under the mountains, the Lötschberg Basistunnel and then the Simplon tunnel in Italy. ( if you are coming from Zermatt or Lac Leman area, you would only use the Simplon tunnel).
To get to Lake Como, there are several routes. Assuming your destination is a small town such as Varenna or Bellagio rather than the two of Como, you can go:
To Milan on the direct line from Zurich (or Luzern) via the Gotthard route. Another long tunnel (Gotthard Basistunnel) unless you route via Göschenin on the old Gotthard route,mwhichnis a few short tunnels but is much more scenic. At Milan you change to another train for the one-hour ride to Varenna. If Bellagio is your goal, you need to change to a ferry as the train does not go there.
Or to Varenna from the north, via the Bernina Pass route from Chur or St. Moritz to Tirano, changing there to an Italian train to Varenna. The Bernina route is the most scenic as it truly goes over the Alps, not under them in a tunnel.
Varenna (or Bellagio) by this (Bernina) route would be my choice. We like Albergo Milano, in a lakefront room. Have never visited Bellagio somI cannot compare them.