Originally Posted by A Harris
Jackets meant for actual motorcycle riding have to fit tight in the waist so they don't puff up like a balloon in the wind. And they have to be big in the chest and shoulders so they are comfortable in the riding position. These are advantages when you are riding but not so much if you are just looking for streetwear.
More importantly, in the case of a fall, the loose folds in the leather of an ill fitting jacket will bunch up causing the leather to tear very quickly. Also, you don't want the jacket to ride up whilst sliding on asphalt, so it needs to be tight at the waist. You want a motorcycle jacket to be snug everywhere. Most real jackets have articulated shoulders/sleeves so that they are comfortable in the riding position. A natural consequence is that they are less comfortable in the standing position. Also, contrary to some of the opinions of others, I've found that motorcycle jackets are shorter than regular jackets, particularly in the front. This is another consideration for comfort in the riding position.
I would never buy a real motorcycle jacket for casual use. Go with a fashion company with a motorcycle look. The leather on a real motorcycle jacket is extremely heavy. Wearing a Vanson feels like donning the lead vest at the dentist's office. Great for safety, but not the best to walk around in. Further, I don't find their cuts [Vanson in particular] very flattering. I believe the general consensus is that Vanson is made for the prototypical American middle aged man. Those looking for a more slimmer more modern fit tend to look towards Italian or Japanese makers, such as Dainese and Kushitani.