It seems that both are practical units that are useful in employment. I've only done 3230, but I thought it was quite a good unit for this. You spend most of the course doing a group assignment in which apply valuation methods to estimate the worth of a company selected from the ASX (possible downside if you can't find a good group - the assignment is worth 50%, although I think they mark it fairly leniently). Tutorials are pretty much your standard finance ones where you go over the weekly questions, in this unit a lot of the questions look at case studies (balance sheets etc.) and sort of bridge the gap between accounting and finance. I don't think you need any accounting knowledge to do well (I got a D without any acc. units except the 1st year one, and other people went ok without accounting skills) but it may help a bit.
Haven't done 3540, but there is a review up for it. I've heard it's a harder unit, although in my experience frequent assessments aren't always bad - means far less to cram at the end of the semester, and if you've kept up the work you'll probably be ok. Also looks like more mathsy/calculations type work, but some people find that easier anyway.