I havent been impressed with the 500 personally... however i also dont own one, but i have worked on quite a few of them at the last shop i worked at... the fanboys all say its better than a 661... which i may be biased here, but, none of them i have run have come close to a 661... and i personally have a ported 661

so that probably doesnt help matters, but i also have a 460 big bore that i am still breaking in, and it gives that ported 661 a run for its money... i think it might have more oomph where it matters for long bar work than a 500...