I have mixed feelings on this topic now. If you'd asked me 6 months ago, I would've said everything that everyone above me is saying, "These exercises are good when performed properly".
Well, I can confidently say that I've been performing these exercises properly for several years now.....but I may never do them again. Despite all of my efforts of proper form, weight control, mobility, core strength, etc....I find myself with an injury that has been caused by excess stress on the back and spine.
No matter how strong your core is or how perfect your form is, you're still putting load on your spine. And lots of load over a lot of time can lead to disc degeneration and injury.
Overall, I say they are both good exercises when done properly for most people. But if you do ever feel discomfort or pain, listen to your body and STOP.