Both, right? Because why would we choose if we can always do and invest in both said altcoins. BNB and ETH has their own distinct utility that makes them useful up to this day because they won't be still alive these days if they don't have that much of utility, and if we're talking about practical then it is really hard not to mention BNB but ETH is also a must sought crypto. Just hodl both because there is indeed a good opportunity in these coins in the coming months and years.