Thanks everyone for the input...
Both the M6 and Activ-L are very popular but both discs have less than 10 years of data. M6 only about 5 years.
Since my problem is at L4/L5, I am leaning more towards the Activ-L at this point because of the Oblique Lateral pararectus approach option in case reposition or revision is needed. If Zeegers says this is a little safer and easier to revise, then I must believe him because he has over 20 years of experience with very minimal problems with ADR, especially with Activ-L.
Although he does use the M6L if he thinks it will be more superior in special circumstances.
I do agree selecting the surgeon is the most important, someone who I feel comfortable and trustworthy.
For those of you with either M6 or ActivL, I hope you are doing great and recovering awesome! I'll keep posting and asking questions until my surgery date comes. Not sure when... we will see. I hope Zeegers don't retire anytime soon
Thanks!