I've worked with AB products (SLC 500 and Micro/ControlLogix) as well as AutomationDirect CLICK and DirectLogix. I would say the *easiest* to use is the CLICK, although it lacks a few features that would make life easier. DirectLogix is the most annoying due to its stack-based programming, but still fairly powerful, and ControlLogix is the most powerful in terms of features and clarity.
My biggest complaint with AB products is the software licensing. It's hugely expensive and painful just to get the RSLogix 5000 on two computers, and there are so many editions of the software, some with limited features, etc. that it becomes a nightmare just to connect to a PLC. I think it would even be OK to charge a bit more for the hardware so they could give the software away free, or at a very reduced rate... I doubt that would hurt their bottom line at all, and it would make lots of people's lives so much easier. Make people happy: they buy more of your products!
I would like to gain experience with the Siemens platform and some others too.
In some cases, I could accomplish much more with a few lines of code (i.e. C, python, etc) in much less space than ladder logic. I've never used structured text in AB (sadly our RSLogix licenses don't allow it), but it would be nice to have a platform that could provide both text-based and ladder code options (hey AutomationDirect, I'm talking to you!).