Going off the DH2 aptitude calculator sheet, assuming you had neither Leadership nor Fellowship (the two always go together), you'd spend 2100 XP to get both talents and another 3600 to max out Command for a total of 5700 XP.
With just Leadership, this drops to 2000 for max Command (assuming you don't start with it) and 1650 for the talents, totaling 3650. To buy everything tied to Leadership, you save 2050 XP by having the Aptitude. That's not really a lot of XP. It's worth noting that if you had Fellowship instead, the cost would be the same, and the Fellowship Aptitude applies to more options and is thus more useful.
Just for grins, if you had both Fellowship and Leadership, you're looking at just 1500 for the talents and 1000 for command, totaling 2500 for a savings of 3200XP. Not a small amount, but not great.
It comes down to a question of how long you expect your character to last. Are you going to get more than 5700XP? You're better off without Leadership because after that, having it doesn't help you at all and only makes other things more expensive.