Newer 3000's have a standard Mini-USB port on them. Older MX3Ks have a notched proprietary cable. I have better luck with the 350, but it's still not always bullet-proof. There's some tough environments that have made them not work. Same with the 400. I have less problems with the 400, simply because it's single commands being issued as opposed to strings of commands. RTI arguably has more reliable RF, but it's really what you're comfortable with.