Berner Oberland

Grindlewald is closer to Jungfrau. Murren is closer to Schiltorn. If you want to split the difference stay in Lauterbrunnen or Wengen.

From Grindelwald, Jungfrau access is easy. The cogwheel train to Kleine Scheidegg leaves near the bottom of the town, near the ski gondola to Männlichen.

Grindelwald, however, sits in a valley parallel and separate from the Lauterbrunnen valley, with the Jungfrau massif forming the divider. The Schilthorn is on the opposite side of the Lauterbrunnen valley, so to get there from Grindewald, you would either need to drive, or ascend to Kleine Scheidegg, back down to Wengen, down to Lauterbrunnen, over and up to Mürren, and from there, up to the Schilthorn. (There's probably some other way via public transportation of which I don't know).

As the other poster noted, Wengen and Lauterbrunnen split the difference. I greatly prefer Grindelwald in the winter (the skiing is far superior to the other side), but Wengen, Mürren et al are probably nicer in the summer.

And just making sure we have our names correct, since this gets frequently confused on this website... Grindelwald is separate from Gimmelwald, the dinky little farming village that Rick Steves for some reason seems to think deserves an entire chapter in his book. Gimmelwald sits a little downslope from Mürren.

Grindelwald to Lauterbrunnen is simpler and less expensive than the up and over and down route.

Just take a train towards Interlaken to the dividing point of the two lines at Zweilütschinen. Off and over to the train from Interlaken to Lauterbrunnen (make sure to get into the bit going towards Lauterbrunnen or you will go straight back to where you came from). Then up the cable car, onto the train and you are in Mürren. Walk through the village to the cable car station and you are up towards the Schilthorn.

Grindelwald is beautiful but it is also tour bus haven. There will be loads and loads of them. If you want to see the Swiss Alps then choose Lauterbrunnen or even better - choose Wengen or Murren where no cars are allowed.

As your touring seems to be focused on the Schilthorn and Jungfraujoch, the most central location would be to stay in Lauterbrunnen, since it's the transportation hub for both sides of the valley. Staying in Grindelwald or Wengen will be closer to the Jungfraujoch, but farther away from the Schilthorn and Mürren (and you'll still have to travel through Lauterbrunnen to reach the latter two sights).

There are no "motels" in Mürren. They have a number of good hotels and I believe some B&B's (haven't checked lately). The guidebook has good listings for accommodations in several towns in the valley.

One point to mention about visiting the Jungfraujoch - be sure to check the weather report first, as if the weather is overcast you won't be able to see much at the top. It's an expensive trip, so always a good idea to get the most value from that trip.