If the PC gets slower on running the program you need to check a few things. All the recording softwares use a lot of RAM and CPU. If your CPU usage at that time is more than 85%, the recording will be slower.
Also, make sure that no other program/software is running in the background ( On windows you can use Task Manager )
I have used ocam,bandi and a few tab recording softwares as well.I prefer tab recording.