Armor placement
Shoulder and elbow armor should stay over the joints when you are in riding position. A back protector is also worth adding if the jacket only ships with foam.
Textile, mesh, or leather
Textile jackets are versatile, mesh jackets are useful in heat, and leather can offer excellent abrasion resistance. The right answer depends on your climate, commute, and tolerance for discomfort.
Fit and retention
Look for waist, arm, and cuff adjustments that keep the jacket from ballooning or rotating. If armor floats away from the impact zones, the jacket is not doing its full job.
Comfort is not vanity. If a jacket is miserable, you will eventually stop wearing it, especially in bad weather or summer heat.