With Collab there's no "fighting your corner". You buy in to the mindset that you have a shared problem and try and work out a shared solution that works for you both. Your solicitors have a personal investment in helping you both achieve that end. If you can't agree through Collab then you must instruct other solicitors.
I think you get better outcomes through Collab than mediation, but it can cost a bit more. It's a much more supported process for you both.
With mediation you have your lawyer advising you in the background, although never at a mediation setting. The mediator should ensure that you get your point across.
Both are purely voluntary. You can't force him to participate in either.
DH and I are getting divorced. DH wants to go down the mediation route because it will be cheaper. I want to do collaboration because I don't think I have the mental strength to properly 'fight my corner' with a neutral mediator hence would like my own solicitor present for the discussions.