even though inuyasha wins most of the time its because...
1) he has tetsuiaga
2) hes the main character so they wanna make him win
3) he has more teamates
4) its just luck
5) on the first battle kagome helped inuyasha by getting the tetsuiaga.
you could see inuyasha was failing miserably on the first batte until he got the tetsuiaga!!!
if you observe when inuyasha and sesshomaru are fighting sesshomaru is stronger !

I agree Sesshomaru is stronger then Inuyasha

Agreed. Sesshomaru is much stronger on his own, no props. Without is friends and props Inuyasha would have been dead long ago.

sesshomaru cuz he's much older , well trained and plus he's full demon ^^

Canonically it has already been stated as fact that Sesshomaru is the most powerful character by the end of the series... he regained his arm and materialized his own sword, getting past his insecurity with Inuyasha's Tetsusaiga and being more willing and compassionate. And he is a full demon lord, as we all know.

Again, I totally agree with Sesshywind. Without Inuyasha's weapons and so called 'friends", he'd be as dead as a doornail. I'm not just picking Sesshy because I despise Inuyasha.