Phone aren't designed to be dropped. That's why there's an entire market out there for cases and protectors. They make your device look more clunky but the do protect well from accidental drops from time to time.
With regards to battery, that's totally dependant on how much you use the device. The more MAH on the battery the longer it will last. But for some perspective you would get more out of a 2300mah checking things occasionally than you would from a 3500mah devices your using constantly.
Unfortunately your question is totally subjective and there is no right or wrong answer.
On Android you can now switch between Dalvik and ART. ART has reported better battery standby time, however not all apps are compatible with ART so you might have to switch it back to use certain applications. Personally I just left mine on Dalvik