I don't think that we can directly compare the two situations:
PICARD: I see. What would you say if I told you that I believed that I was capable of being very much more.
RIKER: Perhaps we should discuss this at your next evaluation.
PICARD: I would appreciate it if we could discuss it now. You see, I feel that I would like to move beyond astrophysics to Engineering or Security, something that might even lead to Command.
RIKER: Frankly, Lieutenant, I don't think that's realistic.
PICARD: Why?
TROI: I really don't think this is the place to be discussing this.
PICARD: Please. This is important to me. I believe that I can do more.
TROI: Hasn't that been the problem all along? Throughout your career you've had lofty goals, but you've never been willing to do what's necessary to attain them.
PICARD: Would that be your evaluation as well, Commander?
RIKER: I think I have to agree with the Counsellor. If you want to get ahead, you have to take chances, stand out in a crowd, get noticed.
PICARD: I see.
RIKER: Now, we don't want to lose you. You're a very good officer.
The above is taking about how you get into Command, basically by showing your leadership potential (Astrophysics is poor, Engineering is good, Security is better).
SISKO: Part of being a captain is knowing when to smile, make the troops happy even when it's the last thing in the world you want to do. Because they're your troops and you have to take care of them.
WORF: Life is a great deal more complicated in this red uniform.
SISKO: Wait till you get four pips on that collar. You'll wish you had gone into botany.
This - by contrast - is taking about the differences in responsiblities of being in Command and being a Security Chief. And suggested being a Science Officer (botany specfically) is a lot less intensive and high level (which is backed up by the first quote) compared to Command.