I've test-driven a Cruze 1LT and a Sonic LT, both with 6-speeds, and I didn't feel the linkage on the Sonic was quite as precise as the Cruze's. I would have no problem living with the Sonic's, but the Cruze's was just so nice.
The thing about the Sonic that bugged me the most was the driver's armrest was mounted too high to comfortably shift, and I don't see any way to adjust it.
As others have said, the Sonic's top gears are the same as the Cruze Eco's, but the Sonic has an even taller final drive. But tire diameter seems to equalize things though because the mph/1000 rpms is pretty much the same. The Cruze LT's 6th gear is the same as the Eco's 5th, with a more even spread below that.