That's probably a straight out lie to say it's better.
Comparing Vivitar RGPRO-648 with Canon 430EX II Speedlite - Photo.net Canon EOS Forum
While it may work, 3rd party manufacturers have to reverse engineer their flashes. This goes for Sigma, Vivitar, Promaster... everyone. I have not heard of Canon licensing their flash technology to anyone yet. What does this mean? Canon's EX line are forwards/backwards compatible but many of the 3rd party flashes do not communicate with newer or older bodies, things get fuddled up.
Not sure who you ordered from, but if they give you the "backordered, but here's 'better deal" runaround, I'd run away.
B&H, one of the most reputable and depended on dealers out there, has the flash in stock, new, legit, and free shipping!
Canon 430EX II Speedlite TTL Shoe-Mount Flash 2805B002 - B&H