yeah, you're right. the basics at H&M are great most of the time. I got 2 jackets from Zara and they rule (Size L fits me perfectly). Zara has great basics too, but in most cases i prefer H&M, whereas Zara has betterlooking "non-basic" items such as jackets or coats.
I think Zara's basics are more suitable for the not-so-casual-outfit. Take their longsleeves for example, compared to H&M's... much thinner fabric, and sewed differently, more to be worn with suit pants that with denim, I think But same is true for almost everything from Zara... outerwear too