Yes, running uphill is a better workout and it feels better on the knees.

why? downhills are free.

Not on your knees. Downhill running (and hiking) is also more anaerobic (stopping your self from falling) than aerobic (working to move up).

If you're stopping yourself from falling when running downhill, you're doing it wrong. You should be "leaning into" the hill, which is counterintuitive and feels like you're going to fall, but is way better for your knees and also faster than stopping yourself.

That only works for some grades. The grades in the Bay Area are pretty steep. If you leaned into the downward slope, you would be on your face in a few seconds.

That's why you should only run down Lombard Street!

You may have just misspoken but it'd be almost impossible to get any anaerobic training out of downhill running. You might be doing some muscle strengthening though.

You can definitely get an anaerobic workout from downhill hiking. Running on pavement not so much, but you do use muscles to keep from falling down.