Which should I buy, WAVES or ETH?
If your not sure which one to go then it is always good to go with both coins because of waves and eth are good coins. You can reduce your future losses when you diversify your funds.
It's too late for waves, remember so many investors are loosing believe in waves platform and so many garbage tokens on the waves platform. Waves smartcontract means nothing. If smartcontract was offering a very easy way to use decentralized exchange of waves and then it will be useless without a lot of demand.
Yes, they need to do something to block fake tokens distributions to all members. If this continues like this then people may lose the interest in this coin.
Bought WAVES and DASH think WAVES can go higher but DASH is safer play?
I don't think any coin is safer in crypto world. But as long as you have diversified then your chances of losing all your investment will reduce.