Gimmelwald was interesting to explore - for a half day, including dinner. It's really tiny. Mürren had many more food options (including a small supermarket) and better quality restaurant food, as well. I agree that while Mürren has many things for tourists, it's not "touristy" in the sense of feeling spoiled. And Gimmelwald is "spoiled" in its own way, with its "honor shop" and other things that wouldn't exist without international tourism.
I was very glad I stayed in Mürren instead of Gimmelwald (or, for that matter, Lauterbrunnen). The views from Mürren are everything they're cracked up to be, and I also enjoyed the convenience of having easy access to both the train and the cable car; they're at opposite ends of town, which only means a 10 minute walk. I stayed at the Hotel Edelweiss, and my single room didn't have a balcony like the larger ones, but had an amazing view straight across the valley to the mountains!
I found that for Swiss hotels, it's very important to e-mail them directly. Rooms that were not shown on their Internet booking sites were available when I contacted the hotels directly, and at often lower prices than on the websites too (remember to specify that you found them in the Rick Steves Switzerland book).
I was also very glad I stayed for 4 nights (3 full days), so that my day of cloudy weather didn't cause problems (I had already gone up the Schilthorn on a sunny day and the Jungfraujoch on a mixed day). So, stay as long as you can spare.