Travis certainly had more featured episodes than Sulu ever got -- by my count, two, whereas Sulu had zero. Having said that, during episodes which did not center upon Travis, his character often receded so far into the background that the only difference between him and an extra was main title billing. Sulu often got little moments that helped define his character in a way that Travis never did -- especially in the third and four seasons of Enterprise
, when he often didn't even have a speaking role.
I suppose you could blame this on Anthony Montgomery's acting -- except that he's been far better and more interesting in other roles on other shows (and in movies). This leads me to believe that the writing staff didn't know how to develop the character.