Wigan fan but I think Powell is great signing for you.
Absolute rock in defence (which I feel Walker has struggled with), doesnt offer too much with the ball, he won’t be scooting (unless it was a Wigan tactics not to run from dummy half).
But what he will give you is an elite attitude, will to win, and probably raise standards at training.
A culture signing which looking at your squad is needed.
In a big intense game, I can see Powell starting and doing the tough stuff then being Walker on.