It is unfair to call Alpha a "version" of S5. It is certainly better than S5. Here is my take :-
1. Exynos 5430 is probably the first 20nm SoC in a commercial device. Advantages over 28nm chips like SD801/805/Exynos52xx are obvious in terms of power efficiency as well as performance, and in benchmarks, Alpha has already proven this. yet to prove its power efficiency though.
2. Lower resolution on this is actually a plus. By doing so, they came closer to what the human eye can notice. Carving for UHD/1440p displays is moving insanely wrong direction. Alpha's display will not be a battery sucker for sure.
3. The above two points imply why Samsung went for a smaller battery. It might have gone the other way as well, keeping a monster battery and losing the elegance.
4. Samsung should refrain itself from using metal elsewhere on the body other than the frame to keep the device safe from mechanical injuries. Yeah, removable battery and back cover make devices more tolerant to drops and falls. More Metal/Unibody is a step away from device's mechanical safety.
5. A dual SIM neo version should be launched soon in emerging markets. probably with a hexa-core 20nm exynos with LTE.
6. Would have been better if it was IP67 certified.
Let's see how this device fares in daily use.