The advantage of using Rock, is that they ship fast to your door by Fedex with no customs or entry charges. And they usually have lowest prices. Autohaus usually has crazy shipping charges. I have used FCP for smaller items as well as when in USA. You have to be careful about customs and entry charges. I was recently charged $30 fee by UPS just to collect $5.00 in tax on an item vendor sent by UPS instead of USPS!
I have bought from Autopartsway, but have had a number of problems, so only go to them if I have to. For that starter, they had a high core charge ($80) and I believe buyer has to pay shipment costs which would be high for such a heavy item. I doubt that dealing with them on a faulty part would be easy either.
I have had no reason to return anything to Rock. Just trying to anticipate how they will handle it. This time I may have to, unless they will allow local shop to repair whatever is wrong with the ACDelco starter. Have to have shop remove it first.