I don't think there is any such thing as a "lower quality" decoder. Less functional, yes, but lower quality. No. As suggested, digital technology is digital technology, and on is on, and off is off. yes is yes and no is no. black is back and white is white. There is no hazy inbetweens when it comes to digital "commands".
Some decoders have a "silent running" function, which uses a higher "frequency" for the DC "pulse waves" that it supplies the motor with, which can elimiate motor "hum". Some of the "less functional" decoders don't have this capability. If your loco is performing like a DC loco on, say, dirty track, then it's probably not the decoder, or maybe it's a loose connection. Also I've found, even though it may be exactly the same loco, with exactly the same mechanism, they can, and do perform differently with regards to speed, smoothness, and noise. Especially the cheaper locos, be they on DC or DCC.
What make/type of decoders are in your other locos?
Also, check to see of your new decoder supports 128 speed steps, and maybe you're using it as 28 speeds steps (or vice-versa), if it's not moving up and down smoothly through the speed steps.