There is nothing wrong with choosing a patron saint who shares your given name. That said, I think the question really ends up being opinion based, since the only rule about choosing a confirmation saint is that they actually need to be a saint (eg you couldn't choose J.R.R. Tolkien as your confirmation saint). I don't think that there really are any pros or cons to choosing a saint who shares your name. If your name is Thomas, for instance, but you admire the Dominican intellectual tradition, you should not be dissuaded from taking Thomas Aquinas as your patron simply because your name is also Thomas.
When I converted from Lutheranism, I took St. Augustine as my patron for myriad reasons, and one of those was actually that my middle name, Austin, is a shortened form of Augustine. I chose him in part because I share a name with him, though not my first name.
Likewise, I don't think someone should feel obliged to take a patron saint who already shares their name. Perhaps Thomas is a convert from Orthodoxy, and in order to show his fidelity to the Pope, he chooses St. Peter as his confirmation saint. He should not feel obliged to pick someone named Thomas instead.
