Logen states that he has no preferred weapon and prefers to be familiar with all types of weapons rather than specialize. Later in the series, we learn that the customs of fighting in the circle mean that combatants must use the weapon their opponent brought rather than their own about half the time. Logen's reluctance to specialize seems to be an adaptation to his frequent fights in the circle.
Much as Logen recalls spending his whole life as a horrible Blood Knight, it's easy to assume that he's exaggerating, or that his misdeeds were actually the Bloody-Nine's. After all, everything we see of Logen tells us that he's a Gentle Giant and a man of honour... until the third book, when he returns to the North, reconnects with some old friends, and starts acting more and more like, well, a horrible Blood Knight, even when he's apparently "himself" and not the Bloody-Nine. And it's not until then that it occurs to you that everything we've seen of Logen happened after he was separated from everything and everyone he'd known - in other words, at a time when he was in a perfect position to reinvent himself as the man he'd always wanted to be. If the book had started an hour earlier, we'd no doubt have gotten a very different first impression of Logen.
