All through the 50's and 60's, Red Heart was the main yarn brand that was readily available. And I used it extensively (I still remember the first variegated yarn - bright reds, blues and yellows) and loved it.
But these days, it seems to me that the Red Heart brand in general has, uh, declined somewhat in quality. The last sweater I made with Red Heart was oddly susceptible to breakage - I've never, ever had that before.
Lion Brand seems to be much better. I would choose Lion over Red Heart every time.
Please remember that I am speaking generally, from my own experience. Others may very well have different povs.
Hope this helps,