I have access to both Amazon Prime Now and Instacart in my market. Prime Now has access to a high-quality local grocery chain, and Instacart has basically everything else including Whole Foods. That local chain is much better in terms of selection and quality than anything Instacart has, especially Whole Foods, which I find to be overpriced for pretty indifferent quality.

Despite that, the service quality from Instacart is so much better than Prime Now that I prefer to use them unless there's something I absolutely cannot get except from that local chain. I'm crossing my fingers hoping that the outcome of Amazon's acquisition is that Instacart loses Whole Foods and the local chain moves over to Instacart, because then I will never order groceries from Prime Now ever again.

By service quality I mean all of these: good judgment in selecting items like produce and meat (although the meat quality from Whole Foods is very inferior), ability to add items before the order is shopped (you can't do that even if you place an order for the _next day_ with Prime Now), ability to cancel or otherwise alter an order (I had to cancel a Prime Now delivery in an emergency, and it required calling customer service), interactivity in selecting substitutions, good judgment in selecting substitutions, and accuracy and granularity of order status page.

I'm not saying I haven't had the occasional bad experience with Instacart on any of those, but they're good enough that I'd trust them to get me the groceries I need before a party I forgot to shop for. Prime Now I wouldn't trust unless I knew I had a good fallback if they mess up.