It's not so much about personal preference, you have to complete all the ground exams before you are allowed to take the CPL skill test. You may start training for the CPL before sitting the ground exams but can't take the skill test until you achieve a full pass in all 14 ATPL exams. As this will take a long time and the CPL training will only take about 4 weeks you have to get the ground exams out the way first as you won't do them all within 4 weeks! Good luck.