Not sure I see how being a pro relates to parallel clamps? I use them because they are faster and I can stand them up when a panel is glued up. I Like that when a panel has two on it you can slide a third under sideways, something bar clamps will not allow. They are just not so damn clumsy. Less prone to damage without cauls, and I can make them work with one hand when needed. I like them, So in summary, I am a pro, and I lie Bessey K bodies. Oh, the shame!
But I am curious about the Bessy I beams I have been doing more doors lately and I like beam clamps on doors, could use some more.