Tho there are other tradeoffs (mainly expected latency).
I had to read this intro 3 times to wrap my brain around the 2.5 negations, just to find out you DO think Walmart is not capable of competing with Amazon :)
I think.
Actually, thinking Walmart is capable does not follow from not thinking they aren't capable. The subject doesn't think they are incapable of giving any hard times. Overall this is perhaps the weakest vote of confidence in Walmart possible, I would read this: "There exists the possibility that Walmart is capable of giving Amazon one or more hard times."
That's the best I can do.
edit: On reflection the word 'thinking' is crucial, because is suggests a level of uncertainty. Without that uncertainty: !(not walmart is not capable) <-> walmart is capable.
When I got my first iPhone I was recommended a Zagg screen protector. I found that Walmart online had the best deal so I ordered it for in-store pickup. I was notified the day it arrived and headed back to the Layaway area. Nobody was there, but there was a little kiosk where I could enter my info and someone would fetch my item for me. Seemed like a very efficient setup. Walk in, get my thing, and leave.
After putting my info into the kiosk and being told my item was on its way, I waited. And waited. And waited. About 15 minutes in, after entering the info into the kiosk again and not getting a response, I called the store and asked for a manager. It took me a minute to get them to understand that I was calling from inside their store to get my item. But finally, they got it and assured me that someone would be bringing out my item shortly.
Another 15 minutes of waiting and I HAD TO CALL THEM AGAIN! And explain, again, that, "Yes, I'm standing inside your store, waiting for the thing I purchased. We talked about this already."
All told, I was probably there for 45 minutes before I got my item. That was the last time I bought something from Walmart.
Now, I'll concede that this was almost 10 years ago and maybe they've changed. But Walmart has never been known for the best customer service, and Amazon is always fantastic when I have to deal with them. So I'm placing my bet on Amazon in this particular race.