The unfortunate fact of the matter is, most 3D design software is quite similar, in that learning the software can require a bit of a learning curve. At first, it is a rather unusual way to design things but once learned can become incredibly powerful and intuitive, especially when jumping from software to software if that is ever required (particularly if you have to write machine code for a CNC mill). My best advice to you is to pick one and simply jump right in and learn it. I know that's probably not helpful, but that's the reality that I faced when choosing design software myself.
Solidworks and AutoCAD are both great, but I personally prefer CATIA (I'm biased, though, as an aerospace engineer, so take this as you will). It is more powerful than Solidworks, and CNC milling can be quite simple if it is used properly. Richard Cozzens' book (http://www.amazon.com/CATIA-V5-Workbook-Release-19/dp/1585035440) is a great beginners resource that walks you through simple projects and it's not too expensive. There's an advanced workbook and an even more basic introduction book that're also not too expensive. There are also plenty of youtube videos that reference CATIA (though this is true for most design software). The Guerilla Guide is great, too (referenced previously) if you want to do some CNC machining.
I like CATIA, but it is expensive and has some odd quirks, and most other software will work just as well. My advice is again to just pick one and learn the basics thoroughly, with budget and range of capabilities being the best guides. Then you can move into more advanced work with the same software.