Pro-Tec probes are inexpensive compared to other probes.
I can get any probe to work, it’s all about the feel and some probes, like the Laurier IBP, has tips that can concentrate energy so well, that you need to lower the intensity and timing. Tapered probes are good for deep hairs. Ballet gold is great for blend. So probes have certain characteristics that are good for the job at hand.
One piece or two? If I want some flexibility for live probing curvy hairs, I will choose a two piece like Pro-Tec or Laurier. If I want some stiffness, I will choose a Ballet one piece. You can bend both types for hard to reach places, but two-piece Lauriers are the best for this task.
Try all probes and get use to feel and performance of all.
The only probe I will not stock in my drawer, is the Pro-Tec size 1. It is way too flimsy. One off insertion or turn of the wrist makes it crump up like a slinky.