Having done both, I can testify that the common denominator here is that people come up to you and say, "I always wanted to do that." As is usually the case, be careful what you wish for. Both activities are labor-intensive, take every ounce of your attention and creativity, and are much, much harder than they look.
Both are also absolutely fulfilling and fun.
I just finished reading "Adland" by ad-agency veteran James Othmer. He points out that though our industry has changed dramatically, people still are attracted to the profession. And there is definitely a dual nature to the advertising profession.
We are constantly weighing the needs of the client against what we know to be the right solution. Dealing with the concrete realities of budgets and the creativity of ideas. It's definitely a balancing act. And great agencies do it effortlessly and selflessly.
Today, ask yourself this: Is your agency putting your best interests forward or just trying to win an award for its work? Is your agency too quick to give in to your demands-- even if it might not be the best thing in the long run? Just like in raising twins, you have to make sure both (client and agency) are heard and needs are met. Otherwise, someone's going to end up in tears.
What do you think makes a great client/agency relationship?

