I was wondering if I should buy a new PC, due to all the issues that Mac has with OpenGL and rendering.
This doesn't seem like a good question to post on stack exchange. It's very subjective and not a problem with Blender itself, and most certainly one that is bound to be very controversial. A more acceptable question form would be something along the lines "I do certain tasks in certain area. With \$\$\$ budget what would be advised, upgrading my current computer with certain specs or buying a new one? With which components?"
What do you use Blender for? 3D modelling, animation, rendering, game development, product or industrial design, assets development, environments, architecture?
Personal subjective opinion: If you are really considering buying a new machine I would advise to go with a PC. Not only are you not bound by Mac pre configured setups, or limited drivers, you also get to choose what hardware you want. You can later decide what operating system to use, Windows, Linux (or even build a "hackintosh" if you desire). Blender is commonly said to run better under Linux, which is better optimized and consumes less resources.
If you plan on rendering a lot with Cycles, and your budget allows, a good NVIdia graphics card is advised as opposed to AMD or Intel integrated.