Cash is better. If you use cash, the store will generally deduct the net tax refund directly from the amount of your purchase (they don’t have to pay tax), which saves you the tax refund step. But it’s best not to bring so much cash with you when going out, it’s not safe. And credit card tax refund is not very troublesome, but sometimes you have to queue up to get the tax refund form, and then go to the airport to refund the tax.