In my opinion, Van's a better character than Bit. I'm not even going to go into their piloting skills now, since it really doesn't matter. Van's character is a lot deeper than Bit's. He has had to deal with a lot of tragedies and hardships, so he obviously changes and matures (he's in the middle of a war in CC and a crisis in GF, so what do you expect?). Bit doesn't change much during NCZ. He does become more...serious in his battles, but he doesn't change nearly as much as Van does.

Van started out as a carefree kid who wasn't worried about anything, especially about the war. All he wanted was to become a great Zoid pilot like his father was (and he did. Van is probably the best pilot of all time). After time, he comes to really care about his best friends Zeke and Fiona. Moonbay and Irvine hang around him because they like him. Van helps everyone he meets realize the more important things in life. Fiona told him that when she and Zeke were helping the Shield Liger evolve into the Blade Liger. What's special about Van is that he's not afraid to let his feelings show. He cried when he was frustrated about that Imperial soldier he helped out destroyed some of New Helic City. It was his feelings that helped the Shield Liger make the final change into the Blade Liger. Van's feelings saved Zeke from the rare hertz. You can see the changes in Van all throughout CC.

In GF, Van doesn't mature much, but he does become very, very determined to not let his friends get hurt. Thomas didn't like Van very much when they first met (because of his crush on Fiona), but in the episode "The Invisible Enemy", they helped each other out and became friends quickly after that. You can see the small changes in Van's behavior as GF progresses (as well as the improvements in his piloting skills). Towards the end, you can see how much Van has affected the people around him, especially his close friends (Zeke, Fiona, Moonbay, Irvine), who are willing to risk their lives, or even die, for him.

Now for NCZ. Bit started out as a cocky junk dealer. He only got into Zoid battles and got to pilot the Liger Zero because of an accident. At first, he isn't too serious about battles, but he does go all-out in them. He seems to have fun battling. When he loses to Jack, he decides to become more serious, and he does. That's the only real major change in him. He still is cocky and ambitious (and funny). The final fight with Vega...Bit did win, but he still doesn't really change much in the series. I mean, even if Bit did lose, it wouldn't really matter. He could always try again. If Van lost the battle with the Death Saurer, he would have been killed. Plus, the world would have been destroyed. Van was under a lot more pressure than Bit and I'm amazed that he didn't mess up. As for Bit...sure, it was a good accompishment to beat Vega and win the Royal Cup, but Van saved the world (twice, but they haven't finished GF yet).

Now I'll go into their piloting skills a little bit. Bit's not that great of a pilot compared to Van. The Liger Zero saves Bit a lot during NCZ, but even without Zeke, Van's a great pilot (in GF, that is). Van's probably the best pilot who ever lived. Bit may seem like a good pilot, but the battles are not as dangerous as they are in CC/GF. There are rules, and it's usually three on three. Since the Liger Zero is a great Zoid, Bit can just go into battles and beat everyone (though he has trouble with Vega, but that's different. I don't think he really won because Vega passed out from the stress of the battle since he's so young.). Van, on the other hand, has to win to survive. If he lost, he would most likely be killed. Plus, there weren't any rules back then (like one that doesn't allow pilots to aim for the cockpit). So Van's battles are a lot more dangerous, and he could be fighting a ton of opponents at once. If you really think about it, you'll realize that Van is a better pilot than Bit. And as I've explained, Van's character is a lot deeper than Bit's, and he's a better pilot than Bit. Some people may not think so, but those people probably haven't seen all of CC and GF.