Oberland - where to stay for a second trip?

Are you in to hiking or you just want to do the touristy viewpoints?

I can do gentle hiking -- Keine Sheidigg was ideal, for example.

To get to the "other" side of the mountains for you to explore, by which I'm assuming you mean Grindelwald you go through Lauterbrunnen to connect to the broader region. From Wengen to Lauterbrunnen is 13 minutes. From Mürren to Lauterbrunnen is 22 minutes, so you're talking about an additional 9 minutes each way.

If convenience is your top priority and seeing the Grindewald area, then you can stay in Grindelwald. It's VERY different vibes than Mürren. Personally if I had 3 more nights to enjoy the area again, I might do 1 day exploring the Grindelwald region and then use the other days to do more around Mürren that maybe you didn't get to do - The easy walk down to Gimmelwald, the easy Blumental Trail from Allmendhubel to Mürren, the easy walk from Winteregg to Grutschalp. There is plenty to enjoy without focusing simply on the "big name" things like Grindelwald First, which is absolutely swarming with people. The lines to get on the cable car this summer to go up there were stretching all the way down the road in town.

Or am I overestimating distances so that murren would be just fine?

You can look at SBB to see travel times.

Checking just how long it takes to get to Lauterbrunnen doesn’t really do it, since that is just part of the journey and will not give you an accurate read on total travel time. I suggest you enter where you are thinking of staying overnight and then your actual destination for the day. I am choosing Grindelwald as an example...if you want to go up First mountain then you can choose that as a destination.

Mürren - Grindelwald = 1 hr 12 min to 1 hr 19 min (time variation is between going via Grütschalp or via Stechelberg)

Wengen - Grindelwald = 55 min to 59 min (going over Männlichen vs going via Lauterbrunnen by train). Going over Männlichen will be considerably more expensive, unless you have a pass such as the BO pass.

So, you are correct Lisa, to explore the Grindelwald area from Mürren or Wengen will add two to three hours of travel time to your day. But, since you have been there before, you know that this ‘travel time’ is actually very beautiful - you will be traveling around a very scenic location!

The very simple remedy to avoid crowds is to get an early start. This is consistently the same everywhere. Maybe it is not always so easy to get up just a little bit earlier, but it will pay off in being able to enjoy the mountain lifts before they get really busy.

If the walk from First mountain to Bachalpsee appeals to you (take a look at it, perhaps it is more difficult than you want, but remember you can always stop and rest along the way and just take your time - but be realistic about your own hiking abilities and desires) you can avoid the crowds by going up as soon as it opens. Do the hike right away when you get to the gondola station at the top, and spend time exploring the Cliff Walk and maybe getting a snack or meal after your hike and not before.

If you're concerned about travel times, you could consider staying in Lauterbrunnen. While it doesn't have the same incredible views as Wengen or Mürren, it's the transportation hub for the valley and easy to get from there to either side of the valley. I stayed in Lauterbrunnen last time and wasn't concerned about the views, as I'm only at the hotel in the evening to eat & sleep. I'm out enjoying the scenery and views during the day. As you were impressed with Mürren, you could stay there and just plan your touring around the travel times from there. It's not a long trip down to Lauterbrunnen. If you want something a bit more informal and quiet, you could also look at Gimmelwald (just down the hill from Mürren).

You could certainly stay in Wengen again, especially if the sights you want to see are on that side of the valley.