I haven't used TurboCNC for a number of years now. IT did have pauses in it was you stated. I understand this to be with a lack of look ahead functionality.
MAch does have look ahead and is very smooth. You can download Mach and fun it with out a licence file. It will limit you to about 100 lines though. That should be enough for you to evaluate its performance.
One thing to note is that it needs XP and a machine speed around 1GHz