I did Revs 3/4 and Economics 1/2 this year. I found both manageable in terms of difficulty.
For Revs, there was a lot of reading to do outside of class time and memorizing dates

. Though it's relatively content heavy and in-depth, the content isn't hard to pick up - understanding events, it's just dedication and effort. I had an amazing teacher for this subject, who made the classes lively and interesting

.
For Economics, it requires more conceptual understanding, as there are many concepts. Though it's really applicable in real life, there is so much to learn. I personally didn't find it hard because I covered the 3/4 material in year 10.
They are both great subjects, but your subject choice should depend on why you are choosing the subject for. Easiness/least stressful? Most interesting ( personal choice)? Most relevant to uni course/career? Easiest to get a high score? Probably only you can answer most of these questions. History Revs or Further is a good choice if you had little experience in these subjects. In humanities subjects, a good teacher is important because they can give you constructive feedback in order to do well.