The 61 would be my choice. It should give performance roughly equivalent to the 46 2 stroke and be lighter and less expensive than the 70. Remember, you still have to buy the servos, switch, battery(s) prop and spinner within your $300 budget.
I should have clarified, I meant only the transmitter preferably with a receiver and a engine for $300. I imagine the rest will add $100 (i hope its not much more) or so on top of that. it will be more like $400 for everything for the kit +cost of kit-$100 = $500 total. If I have enough Id like a 4 stroke but Ill probably have to settle with a 2 stroke
Mike