Hardware store tubing is cheap vinyl tubing- it works, but kinks very easily (doesn't make tight bends well at all), it clouds very easily and is very thin walled (causing the kinking issue). It's relatively cheap, but at around $0.60-$0.70 a foot, you are better off spending another $1/ft for some good tubing (PrimoFlex is around $1.70-$2/ft on most sites).
Cheap tubing works fine for mocking up a loop, but there's no way I'd use it for a loop I'd build. It works great on a budget, but when it comes to watercooling, the extra $5 is worth the cost.
Don't get me wrong- the first few years I watercooled, I only used the hardware store tubing. It worked, but it does get unsightly fairly quick, unless you run some kind of colored additive in your loop (which we usually discourage- dye is fairly safe vs. 'coolants')..even then, it stains pretty easily.
As time has gone on, there has been more demand for the colored, UV reactive and enthusiast grade tubing we see today. Some of it is ridiculously priced at around $3 a foot. Most brands are relatively good and there are some that are slightly different at flexing tight bends vs. others. I've used Tygon and Feser tubing for the most part with a slight preference for Tygon. I'm going to try my luck with PrimoChill in my current project, so I'll be able to tell how that works out.