Going off what TheatreHead said, the way I perform varies a bit depending on the situation. I perform walk around magic on a bi-weekly basis at a restaurant, so I get tons of opportunities to try out new patter, performance styles, ect. I've found that depending on how my audience is reacting kind of determines how I perform, whether it be content or length. I usually open with a quick rubberband routine of CMH, 2 into 1, band through thumb, and then up the nose. If my audience is enjoying it and having fun, I then segue into a card routine. If they are kind of like "eh,ok..." Then after I snort I simply thank them for their time and walk away, they clearly were not enjoying it (as to whose fault that is...that's a whole new discussion.)
How I perform...hmmmm. I like to say I perform in a fun and friendly way, that gets people involved, and doesn't present the magic as a challenge, but rather as a way for all of us to have fun. I do my best to make the magic happen in their hands, because it's soooo much stronger that way. As for "spectacle or substance" I'm not really sure. Sure people like to say they are deep and work out every little kink in their act when they don't (guilty), but I don't think it's a bad thing to admit you don't do that, because that could give you the kick in the pants you need. I'm not sure what you mean by "substance" beyond "pick a card...here it is." TheareHead brought up his themes of fate, chance and all that, but does that seem "going too deep" like you said in your original post? I perform Anniversary Waltz whenever I can, because the reactions are great and it leaves them with something memorable. I've been testing out different types of presentations with the effect, and each one has garnered solid reactions. I think the whole "you were once on different paths of life" style goes pretty well, and that seems pretty deep too.
Why I perform. This will be two sections. One is why I perform, period. The other is why I perform the way I do.
I perform because I enjoy seeing the excitement in people's faces, or the astonishment one gets when they witness what just happened. I love seeing the reaction's and knowing "I did that." (Yes, I'm thinking of myself here.) I also love (always have) being in the limelight, having people watch me, know me, interacting with people. Magic is a great medium for that drive of mine, and I just have so much fun with it.
2. I perform the way I do because I want us all to have fun. I hate when people sit back after an effect and try to see how it's done or see how they were fooled rather than appreciate what just happened. I don't like magic being presented as a challenge of me vs. them, I like it to be me providing entertainment for everyone. They have fun and are amazed, and I get to bathe in the spotlight, it's clearly a win win for everybody.