Again I work in CAD everyday of my life... so difficulty to use is not a problem for me.
I also started jewelry design with an extensive engineering based CAD background. For jewelry design, I use a combination of SolidWorks and 3DCoat. Although my wife and I began our jewelry business in 1987, I began using SolidWorks in 1999 as a tool for jewelry design. I also have a copy of Rhino and have used 3Design and Artcam. As with anything, the key is to keep learning the details of the software. If you are proficient with SolidWorks, then start with SolidWorks.
The advantage of SolidWorks is the ability to control geometry through a parametric workflow. Swapping between SolidWorks and Rhino is straightforward when files are saved in the correct format. SolidWorks is a very mature CAD package and has an extensive user base. The disadvantage of SolidWorks is that it can be difficult to render organic or sculpted designs. A second disadvantage is it does not have a general smoothing option. A third disadvantage is that it does not have a library of parts for jewelry. Rhino has neither a library of jewelry parts or a general smoothing option.
SolidWorks' interface is based on engineering graphics (i.e. drafting). (see Engineering Graphics, Giesecks, et.al. 1975). If you were trained in drafting, then you will believe this is a natural interface for design. If you are more of a sculptor, you will likely hate this interface. Matrix and 3Design have a user interface designed specifically for jewelry.
The advantage of jewelry specific CAD tools (3Design, Matrix, etc) is their library of findings, shanks, and stone shapes. As has already been stated in this thread, too much jewelry specific user interface can limit creativity.
For sculpting and part smoothing, I use 3DCoat. My workflow is: 1) start with the geometry using SolidWorks, 2) export to .STL, 3) import into 3DCoat, 4) add sculpting, texture, and part adjustments, 5) export back to .stl for printing. 3DCoat also has a nice wrap tool to allow you to wrap a flat ring.
My wife is a gem cutter, so we often work with her unique stone designs that are not typically found in CAD libraries. We use a David 3D scanner to import scans of stones and other objects. 3DCoat works very well with imported 3D scans. SolidWorks is behind on their ability to work with scanned imports.
If budget is an issue in your selection of tools, then a combination of 3DCoat with Rhino may be your most economical path. Since you are already a SolidWorks user, you may want to consider OnShape. An advantage of OnShape is that you can work from a web browser so you do not have to have an expensive workstation. 3DCoat will require a fast computer maxed out with memory and GPU.
I also have a Wacom touch screen and a 3DConnexion space ball. While these are not essential for SolidWorks or Rhino, they are a big help with 3DCoat. www.attawaygems.com