Many have different pressure ratings and are designed with different flow rates in mind. For example MTM has two different versions. One optimized for low flow electric pressure washers and the other for gas. The high pressure 5,000psi one performs worse than the one rated for 2,600psi with my 1,700 psi unit (I've used both). I'm not sure what the torq canon is rated at or if they have different ones. I do notice a difference with the $40 one I got on Amazon and the MTM, mainly more consistent flow patterns.
Also, the company that makes the MTM came out with a new one called the PF22 a couple weeks ago. Costs $100 and you can change the spray pattern from horizontal to vertical (I like horizontal more).