I would say for starting a first robotics lego league is going to be easier to access because they build a smaller robot out of legos, plus the "season" starts in the Fall vs. January for First robotics league.
I've coached a First team that has qualified to go to worlds the last four years and been on the Einstein field once in that time. I think you'd learn a few things
- robots are built to solve problems and the most technically complex and advanced robots don't always solve problem better than simple elegant designs.
- Robots involve multiple skills and usually get built by teams where members are specialists in specific fields. Some people will understand all of the robot sub systems but