If you could replace the balljoints separately then you would be less likely to need the tracking doing afterwards.
When changing both arms you would normally need the tracking adjusting.
I've also found that some balljoints on cheaper arms last such a short amount of time that the rest of the arm is fine even when the balljoint starts knocking. It's a bit of roulette with cheap parts.
If you could replace the balljoints separately then you would be less likely to need the tracking doing afterwards.
When changing both arms you would normally need the tracking adjusting.
I've also found that some balljoints on cheaper arms last such a short amount of time that the rest of the arm is fine even when the balljoint starts knocking. It's a bit of roulette with cheap parts.