The way I understand things, the anterior approach has received a lot of attention in recent years, and a lot of surgeons have begun to learn that approach. There seems to be a transition period when surgeons who have been doing the "older" posterior approach and are learning the "new" anterior approach ...(I use quotation marks because apparently all these approaches have been around for a long time.)
During that transition time, surgeons might operate using different approaches ... I think at some point, surgeons settle on a way that feels most comfortable and pretty much stay with that approach, tweaking it and improving it along the way.
You might want to ask your surgeon how many "anterior" approach surgeries he has done vs. using another approach. Speaking personally I would NOT want to be among the first 100 cases of a surgeon who is shifting to the anterior approach (or probably any new approach). But that's just me.
You can literally ask your surgeon for a recommendation and why they use both approaches. You can ask how many posterior vs. anterior surgeries the surgeon has done. They'll know that info off the top of their heads, and it's not considered rude to ask.