I'd rather have Costa leading my line than Giroud. He bullies defenders through his work-rate and aggression on the pitch, and he's a lot more mobile than Giroud which would work perfectly if he was being supplied by Sanchez, Walcott, Cazorla, Ramsey, Ox etc. Giroud just isn't as sharp and is too slow.
In regards to the best shot conversion rate, just to clear it up once and for all, the latest statistics show Costa ahead of Giroud, but only by one place:
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Was very surprised to Jon Walters top the list to be honest.