that little squiggle is actually matched to the output of the nRF24XX IC, It's a part of the reference design and every board uses the same parts in pretty much the same configuration. it also is of a type that doesn't rely as much as other types of antenna's do on a good ground plane or counterpoise for effective radiation. The rubber duck type of antenna (flexible or otherwise) is only matched to the transmitter when there is a minimum of 1/4 wavelength radius of metal perpendicular to the antenna and extending for 360 degree's around it. If the metallic area is larger that's better if it is irregular the radiation will favor a path along the long axis of the metal acting as a ground plane or counterpoise. My answer is to use the cheap ones and delegate control of them to a bus controlled processor. The reasoning is that I can get the transmitter as high as necessary while not loosing performance to cabling, either control or RF. Long wires on the SPI bus are a no-no a most strict no-no and any type of usable coax ( not limited by size) is just as bad. The other issue is that other SPI devices will suffer too. So when I need to send a message it has an address too. Much easier that way and I can change between any of the protocols that way becausee the transmitter has some smarts too.