I think the best choice between bnb and eth is bnb, because I myself am more interested in coins that are relatively new like bnb, besides that bnb is superior in gas fees which are much cheaper than eth
if I collect one of those coins, I will start from BNB too. the reason is, BNB has the same potential or even more than current ethereum, and it's still pretty cheap. maybe having around 10 or 20 BNB in the wallet could be a very good thing in the future.
I think both are worth investing and I am holding both of them but both are different networks, BNB has attracted huge investment during the past one year and it will continue attracting new project as being best alternative of Ethereum with much lower cost. Ethereum 2.0 is going to be fully implemented in the next few months which hopefully will reduce transaction fee significantly.