I have run a spool and diff in my 1/12. I feel the spool is faster and easier to drive when the bite is high. It is very hard to drive with the spool in lower traction. I did find you have to run the car overall softer with a spool. You can not just swap out the diff for a spool. I have a separate center shock built to run with the spool as well as softer front and side springs. So for me, I run ball diff in lower bite and spool in higher bite. I have the X-ray gear diff on order so as soon as it’s available, I am going to try that as well. I think it will be a really good compromise.