Stiff is good on a leather jacket made specifically for motorcycles. It means the leather is thick (which it usually is not on other leather jackets). And that means that leather will scrape off in the event of a wreck, leaving your skin intact. Thinner leather means less sliding distance before you begin to lose skin, and vice versa.
As it stretches from the effect of you wearing it and moving around, the leather will become more supple. You will also get used to the shape of the jacket. Bear in mind you don't need to move around much when you're riding, as long as you can move your head freely and reach the controls comfortably. You don't need to be able to do gymnastics in the jacket or put both your legs behind your head. Unless you're stunting :)
One other thing to look out for is impact-protective armor on the elbows, shoulders, and back. This is really important to keep joints and bones intact in a wreck. If the jacket doesn't have armor in these areas, it should at have pockets so you can buy and insert armor.
Good luck! Happy riding.
Don't think about the jacket. Think about your pants and your shirt. Because it is a jacket, people will actually look forward to seeing it on you. No one will really think about how many jackets you have or whether or not you wear the same one over and over again because.... it just a jacket.
Depending on the color, wear nice fitting jeans and slacks with the jacket. Make sure these pants fit you perfectly though. No bagginess. Skinny jeans (which look good on every guy that isn't lanky) and boot cut jeans are nice. Dark denim is better than light. And make sure your dress pants DO NOT HAVE PLEATS.
As far as shirts, the same rules apply, but make sure that they are not too tight (women dont find that attractive, especially if you are not a ripped muscular guy). Red is a powerful color to get more attention, if that is what you want. Yellow and green are colors that will make you appear friendlier. If you are going to wear black, make sure its a black dress shirt as the quality of fabric will be important when worn with the leather jacket. Do not wear white... that's dated.
As for shoes, nice black shoes are best, but also feel free to wear fun shoes that match your personality. After all, you won't be wearing the jacket the entire time when you go out. (And remember, if you are going to someone's house, you need to take it off, otherwise that's rude.)
It's always great when you find the perfect jacket, but make sure you keep your eyes open for other outter wear that is just as awesome.