IronH: Gsmarena have completed some testing between i9505 qualcom s600 quad vs i9500 exynos octa.
exynos octa is marginally faster, while s600 quad has much better battery life. Conclusion is s600 quad is the one to go for because the minimal extra performance exynos quad has isnt worth the rather significant loss of battery life.
phonearena also posted some benchmark comparisons - some benchmarks s600 quad is faster while in others the exynos is faster. Again the scores are pretty close. No battery comparison though.
I disagree. Unless you're going to heavily use 4g. The i9500 is quicker and has much better sound reproduction compared to the i9505
Edit: wait. What is the s600? The i9505?