Too many systems to cover every reason why none shine as well as Graupner and Futaba, but Hitec is having over heating issues with their Rx's causing brown out/glitching... Spektrum also runs into intermittent glitching/range issues as well... Airtronics went out of business leaving limited support through Sanwa (OEM for Airtronics)... there are dozens of other brands distributed out of China, but if you want to have a US based service center and a product without known issues, then the current top 2 choices are Futaba and Graupner IMO. Once Hitec fixes their over heating issues they I would put them right up there with the other 2 brands.

Another cool selling point with Graupner is they sell matched ESC's which can be programmed directly through the Tx without the need for a separate programming card hooked up the ESC. Just to clarify, you still need a separate Rx, the ESC doesn't include a Rx built into it, however Spektrum has recently started making Servos with integrated Rx's built inside them to help reduce weight for stock racing classes. I've seen Spektrum radios do really well on small too medium size tracks, but also seen too many folks have glitching issues on larger tracks.

For a limited budget, my top pick would be the Radiolink RC3S