It reflects poorly on him. With Zuckerberg we know he has no respect for the Wall Street orthodoxy because he steadfastly refuses to wear a suit. I don't care for him personally but I respect the position he seems to be taking.
But Dell is wearing a suit which means that he in some way feels it's necessary to do so. But he does such a bad job of it that even a glance makes it obvious he doesn't know what he's doing. Or the person he paid to get him a suit did a horrible job. Given that he's "running" a $24 billion dollar company I would like to see better attention to detail on a thing that he must think is important, as evidenced by his wearing a suit.
It could just say that he lacks imagination or doesn't feel that his attire is something on which one should spend a lot of mental capital. A suit is practical, easy, and non-threatening and picking up a bunch of cheap ones is a simple way to look professional without a lot of thought. It's really easy to look like a slob in a t-shirt and jeans and I suspect that a lot of SV CEOs put a deceptive amount of effort into their laid-back appearance.
It's worth noting that Dell is a Texas company, and the t-shirt and jeans look is still a pretty specifically SV trend.
