My personal view which is biased since I am a long term hodler of bts and want it to succeed is that bts is way undervalued and hence a better investment at this price.

On the other side steem is in a very bullish trend and no one knows when this will / if end. Steem may be worth billions one day.

However based on my fundamentals Steem and bitshares serve different things. Steem is for bloggers and bitshares is for traders and savers. Obviously blogging is easier and many people are attracted to steem. Steem may one day worth billions but bitshares may one day attract just a small portion of financial derivatives and worth trillions..It all depends on the investment time horizon.
Many people also forget that there are a lot of unbanked people there who need decentralized market pegged assets that bitshares offers. Many people also live in countries with capital controls. They are not anymore in charge of their financials and their life savings are threatened by bad Government and Banks decisions. Bitshares can serve those people today. Not tomorrow.Today!

Steem has also the potential for stable bitassets such as the Steemdollar. But this peg has to be proven before people convert their life savings in steem dollars. Don't forget that steem dollars have so far ranged between $0.7 - $1.7 (I think)..Bitusd on the other hand is holding the peg of at least $1 for more than 2 years now. So from my perspective I feel safer to hold bitassets in bitshares than steemdollars.

Trading wise steem just had a huge rise within a very short period. A correction may come soon. Bitshares has been on free fall from a long time ago.I feel that the odds of x10 the current price between steem and bts is in favor of bts..

Just my view. Don't take it as an expert's advice. After all I have been losing my money for holding bts for the last two years...:)