The "right" jacket depends on your body type and how you plan to wear it.
Prioritize the shoulders—the seams should align exactly with the edge of your shoulder bones. Sleeves should reach your wrist bone, and the body should be snug but allow you to move your arms freely.
Look for Full Grain or Top Grain leather; these are the highest grades and will age well. Avoid "Genuine Leather" labels, which often indicate lower-quality, processed hides.