On the plus side of the new Futaba 4PX is that you can use almost any S-FHSS receiver which saves you a lot of money since they run between $30 to $50.
I also have and use the Futaba 4PL for my crawlers and use their little 6 channel park flyer receiver. Futaba also has a S-FHSS receiver with no external antenna, about $35.
However, the initial cost is $220 more than a Spektrum DX4R $550 vs $330.