I have seen many PoS coins decline in value over time, making your stakes less profitable than ever.
However, even though this happens, there are a very few coins that prove to become worth to hold for the long term.
Nevertheless, I would like to know which PoS would be best to invest into these days, according to market movement. I'm always on the look for good PoS coins to put my money into, and make my profits grow for the long term.

The market of POS coins now is too hampered and most of the people there are getting a huge amount of loss. From my side I think that a person should invest inn bitcoin for now as it is the all time best crypto currency and also has a good value growth rate. It is the most fast increasing crypto currency and will also become a future currency after some time.
Most of the people try to invest inn new ICOs and think that the coin will get a very high value in just sometime but tis does not happen and they face a loss. So, try to invest in trusted currency and earn better from it.
If you focus on low sat coins, they don't have far to fall, and it's a way to mine bitcoin on computers that are essentially free. Plus, it helps add free heat in winter. It's really a win win situation. You can always sell the staked coins for LTC or DOGE if they fall too low.