You can't compare onecnc Express which only has 2.5d features to Rhinocam which has basic 3d features (CAM). While you could get by with express you really need advantage. Rhinocam (VM basic) only gives you horizontal roughing, horizontal and parallel finishing. Advantage will give you Planar (horizontal) and also Z-level roughing and finishing that I use a lot especially for doing the sides of necks ala Dana B. Onecnc's CAM is unbelievably easy to use but still offers tons of ways to tweak and control it. The simulation and rest robot are an order of magniture better than VM but it has stuff which is usable. I spend most of my time modeling and when I use the CAM features it's mostly to play what-if games to figure out the best way to machine something. Otherwise its easy to use and rock solid.
As I said in the other thread there is an benefit to staying in what acts like one software package. I have not used Rhinocam so I don't know how good that integration is but I suspect it's fine. I import geometry (curves) into Onecnc from Rhino without issues also. I prefer to do surfaces and solids (3d stuff) in Onecnc because the quality is vastly better although with wood we can sand away a wrinkle caused by a modeling distortion if its in the right place. You would need Professional to do surfaces & solids in Onecnc or you can use Rhino and sand a little more.
I just starting with CAD/CAM and guitars a little over a year ago. Onecnc's product has enabled me to move pretty fast. I get no consideration whatsoever from them, I'm just a customer. It isn't perfect, as with any software I have my "list" but there's nothing that stops me from doing whatever I need to do. When I had some early issues with the newly released XR the head of the company called me from Australia a couple of times to make sure they understood my issue and then to follow up that they had fixed it. The people in the states do the same thing. I can assure you that my few thousand bucks isn't going to make anybody call to check. They truely care about happy customers. Their private support forum is absolutely excellent. Answers in hours if not minutes. You'll get a good education from the pros there.
CNC machines are stupid, they are supposed to just do exactly what the program asks of them every time. The power comes with the CAD/CAM software and the creativity of the designer. Spending decent money on the software is important. While I don't think you can go wrong with Onecnc, you will have to use Rhino for artistic curves especially those drawn with splines. I think Rhinocam will also do the job although for clean surfaces/solids my vote is again Onecnc but perhaps there are tricks in Rhino that I'm not using.
We've all been through the decision making you are knee-deep in. If you stick to those two you can't make a "wrong" decision.