I now own a Surfer and I wanted one over a Surf Champ for many of the reasons already stated by others.
* Weight of the Head as I can put it on by myself as the four players are just too heavy for me to wrangle these days.
* Less initial and on going maintenance issues to deal with in a 2 player head vs a 4.
* More artwork on the head of Surfer vs Surf Champ. An interesting note to this is that there are plenty of 2/4 player games with the same amount of artwork on the head (maybe scaled down a bit to fit a 4 player, but basically the same) but Surfer/Surf Champ clearly are way different with Surfer even having one more person in the art (guy surfer).
* We usually throw 1 sizable party a year so having a 2 player to compete with my wife or the next door neighbor just made more sense for me.
** As far as the extra size of the 4 player head a I could accommodate either a 2 or 4 player in my arcade so this was not an issue for me where it could be for others with space that can only fit a 2 player.
Bottom line: Both are great games as they play the same, so it just boils down to your preference which one works best for you in your arcade.
I currently do not have my machine as it is getting paint and bodywork by pinhead52, but hope to be enjoying it sometime late this year and possibly take it to TPF 2016.