Personally, if I were a GM free agent right now... and ALL teams had open GM spots open... I'd rank my top 5 preferences for a career path as this (and why):
1. Yankees (As much cash as you could ever need to put as many great players on the field as you can. Largest market in the world. Biggest media coverage provides more popularity to the team. Recent movement within the organization to not trade away young talent for next to nothing. Younger Steinbrenners easier to work with than George. 2nd largest fanbase of all professional sports teams in the world.)
2. Red Sox (Getting to the point of having an open wallet for payroll like the Yankees. Top 3 fanbase in the MLB - possibly the most loyal and 'rabid'. Fanbase is still hungry for more titles, and constantly in competition with the big dawgs in NY. Biggest movement amongst top franchises of developing form within. A fanbase that would turn you into a God for winning them a title or 3.)
3. Philadelphia (Enough revenue now to put together a roster that can easily compete with the bigger spenders.. and revenue is increasing. New focus on bringing in topnotch players through FA and trades. Still heavily focused on developing topnotch talent through the farm system. Large market with a MASSIVE percentage of rabid sports fans that support the local teams.)
4. LA Angels (Becoming big spenders, showing they are willing to overspend to bring in strong talent. 2nd largest market in the nation, and their in-market rival is declining due to embarrassing owner drama and desperation. A market that will provide you with anything you need revenue-wise as long as you put a competitive team on the field. Located in a region -Southern California- where baseball is still king to young boys. A farm system that is becoming well known for developing strong talent with pitching and catching. Possibly the best manager in all of baseball...with an incredible amount of loyalty to your organization.)
5. Chicago Cubs (3rd largest sports market in the world. An incredibly loyal fanbase. Shown an ability to spend money like water a times. New owner that has proven his desire to build up from within. Top 3 scouting directors in the league, which will only improve scouting abilities as more money is put into player development. The fanbase is so starved for a championship that if you put together a team that would win one, you'd have a job for life no matter how well you do after that. third most popular marketing franchise in the MLB top 10 in all professional sports in the world.)
That's my top 5. To be honest, if the Mets and Dodgers weren't having financial issues with their ownership... I'd rank them higher than the Cubs as well.