Chamakh - Great in the air, good when ball is played to feet and a great finisher. Can also bring others into play and has a great work ethic.
Walcott - Is fast, decent at finishing. Poor control, poor dribbler, poor in the air, poor passer, weak.
And the stats to back it up.
Chamkah's club career stats : 64 goals in 262 games. 1 in 4, most strikers would be proud of that stat. Alot of these where sub apperances too or playing in a mediocre team (Bordeaux)
Walcott's club career stats : 23 goals in 140 games. Majority of these where starts for a top club in England that creates a bucketload of chances.
What more proof is needed? Chamakh is the best striker at Arsenal.