RE: Higher C advantages and disadvantages
This is a great topic.
I'm starting my second season of electric flight. My first set of batteries was 30C, and later I was told that (for pattern flying) 20C was adequate and no need for the extra weight. Due to beginner's misuse (storing at full charge for any period of time) those batteries now perform more like 20C batteries or worse.
What is your planned application, and what's your experience level? Do you want long flights? Higher C batteries will have less resistance to dumping power, so you'll feel more power, but you'll also use the battery faster.
There are many things to consider. For example, 45C batteries at 5000mah can dump 225 amps. That would destroy my motor and my speed controller. I'm limited to maybe 80A continuous and 120A peak. This is why 20C is adequate. So it's important to look at your setup and see if the higher C batteries make sense.
I also chose to use higher voltage (more cells) to save current discharge, which gives me pretty long flights at good power. I could drop from 10S to 8S, but would need to use considerably more current to have the same power, and thus flight times would diminish. If I only wanted 5-6 minutes of all-out flying, a high current (80-100A), 8S setup would save a bunch of weight. 60A on 10S gives me the same performance for 10 minutes. Obviously it adds weight so you have to decide if like how the weight affects the flight characteristics.
My suggestion is to go with 20C. There is a learning curve so I think spending less early on is a good idea (of course I'm stubborn and don't always practice what I preach!) Also, lipos decay over time. Your 45C battery won't perform like 45C in the future, so it's probably a good idea to wait until you need them to buy them.