The game play for both is very different, but really fun. I own Get Famous, and recently purchased Cottage Living.
With Get Famous, you can have the career to make your Sim into a celebrity, and some of the mini games for your Sim going into an acting gig is like Get to Work, and you can either follow the script, or go off of it. Your Sim also has to accomplish things further their career, and tend to start at the bottom.
Cottage Living is kind of living off the grid, meaning you have to rely on mostly what you farm, and what animals you have. You can order your Sims food, but it is mostly living off the land. I haven't played it completely yet, but the world looks good, and the game play adds a new factor to the Sims.
Both packs offer different game play, to me Get famous is pretty active with the tight schedule for your sim, and Cottage Living is more low key, but still a challenge, and fun if you want your Sims to live off the land around them.