Sandi, As others have said - the two towns have a totally different feel. Have you decided where you will be staying? Will you have a car or will you be traveling by train?
If you have a car you can drive into the lauterbrunnen vally as far as stechleberg, and then you would only need to take 1 gondola up to Gimmelwald. If you're traveling by train you can take the train as far as Lauterbrunnen, then bus to Stechleberg, and gondola to Gimmelwald.
We've been to the area twice, and gotten a regional pass both times. We took the train from Lauterbrunnen through Klein Scheidegg to Grindlewald. I really didn't find Grindlewald too interesting (it's much more modern and touristy), but from Grindlewald you can take ski lifts up to First which gives you a great view of that valley, and on the way down you can rent scooters which allow you to take a slow scenic ride among the cows on the way down.
I haven't stayed in Gimmelwald (only hiked to it), but we've stayed in Lauterbrunnen and Murren. I have to say it is a very different experience staying a few thousand feet above the valley floor. There's nothing like it!
No matter where you decide to stay - one way to experience the alps, but cut down on expenses is to only go up one of the "big" mountains - either the Jungfrau (top of Europe) or the Schilthorn (above Gimmelwald). Really you can have a great time, and enjoy the amazing mountains without doing either!