Rob's has been my local grocery store for the past 5 years.
We tried Food Basics around the corner and found the quality of products and selection at No Frills to be much better.
We have recently tried the Loblaws at Maple Leaf Gardens and, as wonderful as it is, we're back shopping at No Frills for our core grocery shop.
No Frills is a perfectly sized grocery store. It's large enough to have a selection, especially of international food for the recent immigrants that leave nearby, but not so large that it takes you 1.5 hours to finish shopping. The prices a reasonable (some items that are exactly the same are more expensive at Loblaws) and because it's in such a busy neighbourhood everything is usually very fresh.
One of the downsides is that there isn't as much effort put into ensuring the shelves are always fully stocked like there is at Loblaws. If you get unlucky you could enter the store when the meat section is completely empty or they're out of the type of bagels you like. It's the chance you take to save a little money compared to the big guys.
One thing I've noticed over the time we have been shopping at Rob's is that the staff is very consistent. There are several cashiers who have been working there for most of the time we've been coming. I swear I've never seen faster grocery store cashiers at any other store.The in-store staff aren't always very helpful and sometimes the store doesn't run as smoothly as a Loblaws.
Summary: Head to Loblaws if you want some freshly-baked Ace Bakery bread or something a little higher end from the butcher or fishmonger, but stick with No Frills for your day-to-day shopping.