RE: Expensive US made vs Chinese Batteries
No, you shouldn't necessarily expect more power from a higher "C" rated battery. IMO, "C" ratings aren't really worth much. They can come in handy when comparing batteries from the same brand, but across brands there is no standard for what the ratings mean. It is supposedly the highest discharge rate that the battery can handle without being damaged. It's not about how many amps or volts you'll get at a lower discharge rate (no one actually runs their batteries at even 20C continuously) but rather how hard the battery can be pushed in testing before its lifespan is significantly reduced. But even that is a pretty vague definition, right? What matters for getting more punch out of your car or plane is the internal resistance of the battery and to a lesser extent, the weight of the battery (lighter vehicle accelerates better).
On the original topic, I'm too cheap to have ever bought the higher end batteries but I have noticed a significant difference between the low end and mid-grade batteries. The first set of lipos I ever bought were the 20c Zippys to run in my Stryker. I liked them fine and could get 10 minute flights and still have about 25% of the charge left. I'd say I got 30-40 cycles out of them before the internal resistance started to rise which reduced my motor RPM to the point that it got hard to takeoff without a big headwind. 1 of the 4 that I ordered was DOA and HK wouldn't replace it unless I shipped it back to them. But for $8 each plus shipping I spent less than half of what a Thunder Power battery would have cost at the time and had 3 usable batteries so I was happy with it. I replaced them with $20 each Power Wing batteries of the same capacity and "C" rating. I could tell an immediate difference in power and after again roughly 30-40 cycles between my Stryker and 450 helicopter I can't tell any difference in the flight characteristics. So I'd say going up to at least the mid grade packs is a good investment, and those who fly a lot and push their batteries hard probably will benefit from the higher end stuff.