Quarter step will be smoother because the steps are smaller, and also because the steps normally have equal torque. With the basic half step mode the torque is not the same on each step and this can lead to vibration or resonance problems. There are ways of doing half step that have equal torque on each step and if your hardware will handle micro-stepping you should be able to do one of these. http://techref.massmind.org/techref/...p/halfstep.htm
Since results will vary depending on the steppers and the machine, the only way to know would be to try both half and quarter.