Easiest to get to from Lake Como

Where on Lake Como? It makes a difference in your route.

As for Wengen or Muerren, they are equally easy or difficult to get to. Wengen is by train from Lauterbrunnen, and Muerren is by a short cable car and a train from Lauterbrunnen on the opposite side of the valley.

Both Wengen and Mürren are very nice with gorgeous views and each is well situated for spectacular hikes near each.
They're each on mountains on opposite sides of the Lauterbrunnen Valley.
My impression of them is that Mürren is a bit more rustic than Wengen. Wengen has a chocolate shop where they make their own chocolates; Mürren does not. I find better quality souvenirs in Wengen than in Mürren. Also, there's a nice jewelry shop in Wengen. Mürren has a town sports and fitness center. Both towns have a grocery store (Co-op) and Wengen also has a small produce-oriented store and also a cheese shop as I recall.

Both towns don't allow cars. If you're driving there, you'll have to park your car in a lot in Lauterbrunnen for Wengen or Mürren, or in Stechelberg for Mürren; both lots are down in the Lauterbrunnen Valley.

Both towns are easy to get to, but Wengen is the easiest.
Starting from Lauterbrunnen:
To get to Wengen you get on the cog rail train from the Lauterbrunnen train station and take it directly up the mountain that's on one side of the valley. Wengen is on the same side as Männlichen, Kleine Scheidegg, and the Jungfrau mountain.
There are two ways to get to Mürren. Mürren is on the same side as Allmendhubel and the Schilthorn.
One way to get to Mürren is to take the cable car in Lauterbrunnen that's across the street from the Lauterbrunnen train station. That cable car takes you up the mountain to Grütschalp. At Grütschalp you switch from the cable car to a train that takes you along the ridge to Mürren at the end of that line.
The other way to get to Mürren is to take the bus from Lauterbrunnen to the Stechelberg cable car station (catch the bus from across the street from the Lauterbrunnen train station). At the Stechelberg cable car station, take the cable car up to Gimmelwald, where you change cable cars to another one that takes you up further to Mürren.

We did this connection in 2016, but it was not necessarily direct and easy.

From anywhere on the east side of Lake Como, you can take a regional Trenord train to Tiranno. The train ends there and you walk across the street to the SBB (Swiss) station to board the amazing Bernina Express. You can either pay a bit extra for the panoramic cars of the Bernina Express or take a regular train for a few francs less. This train will take you to Chur in the Engadine Alps (the part of Switzerland where they speak Romansch).

Once in Chur, you could take trains or drive to anywhere in Switzerland. We stayed overnight in Chur and rented a car and drove to Liechtenstein (nearby, just to say we were there), then to Lucerne for lunch, then to Stechelberg where we caught the cable car to Murren, where we were staying. An easy day's drive.

I have not been to Wengen, but I cannot recommend Murren highly enough.