Help choosing a Canon Speedlite

I'm very much still a beginner with a DSLR. I've fooled around with one for a couple of years, but recently purchased a Canon Rebel 650D with the intention of getting much more serious with photography.

At an outdoor event last night, I truly realized the limitations of the built-in flash (and the kit lens, but that's another story), and I want to get an external flash. Because I am a beginner, I'm leaning towards the Canon Speedlite 430EXII. However, wanting to get the longest life possible out of my purchases, I wonder if spending the extra money on the 600EX-RT would "future-proof" the purchase somewhat.

Should a beginner save the money and go with the 430?