I would suggest that a lot of it would depend on the park's requirements/demands from the soundtrack... Chiapas has several variants on the theme throughout the ride changing along constantly, so IMAScore can do stuff like that, guess though many parks won't desire that level of commitment as it costs top monies...
Klugheim is similar, but nowhere near as catchy imo... The best theme park tunes are the repetitive ones after all, even Tussauds knew that...
A lot of park music relies on the context though, hearing it outside of the ride/park doesn't work really, I thought Blue Fire's soundtrack was iffy for years until I actually heard it properly and it suddenly clicked into place...
IMAScore's success is certainly hard branding and also no doubt being a sudden dedicated signpost for themed music... Parks no longer need to source a composer and just get one company to do it... They saw a gap in the market and it's worked...