Another trade off: Liquid hydrogen is very low density, and requires extremely low temperatures. This means that you need a much bigger tank for a given weigh

Another trade off: Liquid hydrogen is very low density, and requires extremely low temperatures. This means that you need a much bigger tank for a given weight of fuel, and that tank needs to be insulated bc liquid hydrogen must be kept below 33 kelvin. Both of these downsides can come close to negating the upside of increased ISP. But the upside for SLS is that they already had engines that can run on hydrogen. Like you said, trade offs all around