Serious Eats just published the results of their Sriracha taste test. They agreed with you about Shark (came in second to another Thai brand named Polar), but disagreed concerning Sriraja Panich. I am sure that if the rankings were done by someone who is Thai or steeped in Thai food the results might be different.
That's funny. AFAIK Sriraja Panich is the original brand. I would be hard pressed to taste a difference between it and Shark. I alternate brands and they both taste almost exactly the same to me. Both shark and Panich come in various heat levels, with "strong" being the hottest. It sounds like they got the mild one, because their tasters said it wasn't spicy. I only buy "strong". Notice how all the others have crap in them (sodium benzoate, potassium sorbate etc.) including Huy Fong (rooster).