I also prefer Lowe's. I think a big part of it is that, as another company used to advertise, as #2 they have to try harder.
When I lived in a condo, I filled one wall with bookcases -- I didn't have a good place to set up sawhorses, and running a circular saw would probably have violated the lease and definitely have annoyed the neighbors, so I had my 1x12s cut at the store. 6' sides, 2' shelves, held together with countersunk screws.
At a glance, you could spot the bookcases I had cut at Home Despot vs. the ones I had cut at Lowe's -- HD employees had a lot more variance in their definition of "two-foot lengths," so those shelves have a lot more warp and bowing in the sides. The ones cut at Lowe's are closer to square (none of them are especially pretty, because I was going for purely functional; I could have used good hardwwod, cut to spec myself and used glue and dowels, but I was just trying to get my books out of boxes).
Alas, I live in Atlanta, where HD was close to a monopoly for about 20 years. Lowe's has made inroads in the last several years, and in that wonderful way that competition works, they not only came in and did better, but forced Home Depot to get better.
HD is closer, and I go there if I know exactly what I want, but if I need help or advice it's infuriatingly difficult to flag down an orange apron, and unlikely they'll know anything when I do. Lowe's is better for that.
Ace Hardware is better still -- They vary from one to another, but the common factor is that they always seem to have three or four middle-aged guys milling around in the back who, between them, know everything about everything.
A couple of years ago, I was installing a kitchen sink, and the hot water supply line was a serious pain in my butt. The copper pipe was right up against a wood joist. That meant that I couldn't get the torch around to heat evenly and I had to work the torch carefully, because I didn't want to set my house on fire. "Don't set your house on fire" is pretty much my #2 priority for any DIY project. #1 is "Don't get yourself or anyone else killed."
Three failed attempts and three popped solder joints later, after a week of cold showers because I'd had to cut off the hot water at the source, one of the guys at Ace introduced me to the wonders of compression fittings. If I were a better man, I'd remember his name and send him a fruit basket each Christmas.
As variable as they are -- Ace is a franchise -- every Ace location seems to have the aforementioned middle-aged guys, a kid in his late teens or early 20s who's just learning how to cut keys, and a cute teenaged girl working the register. It's almost eerie how consistent that is. They have a smaller selection and higher prices than the big-box stores, but I consider that a premium I pay for the advice.