I can’t weigh in on AVSnap or CAD Freestyle.
Visio is EASY. Easy to make or import icons, photos etc. Builders and architects can send you CAD plans that can be opened by visio, given the layers are in the right format.
The downfall is that if you are going to do any commercial work, CAD is the standard, and providing a DWF file back to the architect will most likely be required.
If you are doing all residential work, your builders will be more than pleased typically with Visio, although you will need their cooperation to get their CAD files formatted properly.
CAD and CAD LT I will group together. You will need a formal class most likely to get this moving properly, and it takes some time. However, being able to work in scale, create an AV layer on the E plan for the architect is huge in commercial work. Having CAD means you also depend less on the builder/architect to send you the right files for Visio import. (We had about a month of back and forth with one builder who got extremely frustrated and finally just told us to work of the pdfs on the website).
CAD is not as artsy, in its basic use, (No pictures, etc, and is less homeowner friendly.
The question is, who are you providing this to? The builder architect? Use CAD.
The project owner and your install team? VIsio would be fine.
I personally would invest in the CAD format as it makes you more viable long term, and homeowners can understand plans without fancy pictures.