You often hear that you have to balance the ratio of pushing to pulling and upper body to lower body to achieve a balanced physique. I disagree. This advice is good for a beginner, but not for intermediate/advanced lifters. Training in an unbalanced or non-symmetrical fashion works great for me.
When you begin training, everything is small and weak. In that case, working everything evenly is a good option. As you become bigger and stronger, however, certain muscles will respond better to training and others will lag behind. If you continue to train in a balanced fashion you'll exaggerate the issue.
Certain muscles, which dominate particular movements, will continue to overpower others and magnify your imbalances. For instance, your anterior delts and triceps might minimize chest stimulation on the bench press. The problem becomes a self-perpetuating cycle and your physique will become increasingly disproportionate.
Once you reach a decent level of muscularity, to achieve symmetry you actually need to train asymmetrically. For example, my biceps and shoulders don't grow well from just being trained with chest and back. Instead, I train them more frequently, which allows for greater overall volume. While chest and back get hit twice per week, I target my rear delts, lateral delts, and biceps four times a week.
Following this approach has paid massive dividends and allowed my shoulders and arms to catch up to my chest and back.