Practically no difference, except a slight trend in likely meaning, but they are used interchangeably a lot still. 'Should be' implies in the current scenario unless otherwise stated (eg, "should be looking ... on Monday") which is very common, while ''should look" implies "from this point forward" or "in the future" rather than "a problem has been identified with past actions" - but this subtle implication is so often neglected, and popular slang often overrides it and even puts it in reverse... So don't read too much into the "official" grammar rules that anyone tells you about this. Anyone who disagrees should propose 1 sentence and scenario where one of these versions applies but the other isn't regularly used also - I bet it can't be done.

"we should be looking for ..." implies you are doing something else at the moment, and you should stop that and look for this. "we should look for ..." does not imply or make any assumption about what you are doing now.

根本问题应该是to do和be doing的区别。 To do-不关乎时间，比如说我看书，我喜欢旅游，查字典等，要么表达这个事情，要么就是说经常做的动作。i read books, i like to do smt. Be doing-关乎时间，可以是正在干的事情或者是在计划内很快要去做的事情。比如我在打字（I am typing), 我要去吃中饭了（i am going to have lunch now)。 所以加上should 的话就是，你应该做....和你本应该在这时候做的区别