One thing I've found, at least in my neighborhood, is the HD has a lot of staff on duty if you need help with anything and for the most part are quite knowlegable, but the store is extremely busy, the parking lot is always full and the line ups at the checkout can be huge so it can take a long time to do any shopping.
On the other hand, the nearby Ronas is practically empty most times with few shoppers, hardly any cars in the lot and no line-ups at the checkout so it makes shopping a breeze and I'm in & out in minutes, but if you need help or have a question, forget about it cause they also have almost no staff working. If you know what you want and where it is, it's great. I wandered around there for 15 minutes a couple weeks ago looking for a salesman in the door section.
I've only been in the new Lowes a couple times (Warden & Eglinton in Scarberia) but it seems really nice and hasn't been crowded at all when I was there but maybe alot of folks haven't found it yet.
Nice to have all 3 to choose from though.