My wife and I live in Minneapolis and our experience over the past 2 years has been basically the same as yours, expect with the companies reversed.

Instacart has been generally top notch in their logistics and customer service. Small issues now and then, but rectified quickly and pro-actively.

Amazon PrimeNow and their Amazon restaurant delivery has been a total mess. Cancelled orders hours after placing them, unexplained delivery glitches where a courier attempts a delivery and leaves with all the merchandise if we don't answer the door knock immediately, etc.

I'm not shy in letting customer service know when there are problems and even the refund process is a mess - we've had charges refunded 3, 4, 5 times (like I spend $100 and they end up refunding me $300 dollars!). Tried to explain to Amazon and get in to crazy unintelligible email threads with offshore service centers.

Finally just gave up on the whole thing with them. Will try again in a couple years and see if things have improved.