which food would you say is best arden grange or aurtarky?

Best for what?  In what way?

IMHO both are good quality foods, my dog did better on Autarky and the price suits me better.

Different foods for different dogs for different pockets for different growth patterns for different tummies, etc. etc. etc.

Try one at a time in a controlled manner and see what suits your dog best.  Register and discuss perhaps?