Did you know that bitcoin pow is somewhat actually green:
https://steemit.com/mining/@sames/bitcoin-mining-pow-the-truth
Basically since most energy produced is usually lost( due to the fact energy can't be stored efficiently or storing energy costs more than making more energy itself ) bitcoin mining gives another use for this energy preventing it from being wasted and giving it value. It also will force miners to use renewable resource because nonrenewable resource will keep on getting expensive. In fact here are already solar bitcoin farms. Yes not the best but the stats saying bitcoin mining is completely wasteful is not true.

Currently POW is better.
While yes POW does seems like an energy waste it not. This work is necessary to make the chain secure. In POS, the stakers who owns 10% of the supply will mint 10% of the supply, and won't cost them anything much.
In, POW you have to battle against everything. You have to buy new miners to keep up, pay electricity, cool the machines, buy new ones.

Pos makes it so that 51 attacks are harder bc they are little their investments on the line. Pow is somewhat even harsher. Not only will their rewards lower if 51% attack done, the coin down=machines useless. This is amplified by asic machines which effectively locks the minier rig to mine only that coin.
Pow can be improved even more by making useful mining aka finding primenumbers.
Plus in hardfork POS is bad.
The large staker who opposes the hardfork keep his coin in the old chain. But in the regular hardfork the staker gets an equal amount of coins. The only way to avoid that is to block those coins which is censorship and centralization