Do you think Settler gets votes more (and it does in my experience) because it's easy to spawn-kill ( especially the cave side base) and camo-snipe, or because it offers a better variety in gameplay?
My snarky comment was more to the REASON people are picking the map (easy to exploit), rather than the game play being similar.
I think both you and Bregman are on to reasons people pick it... variety and simplicity both. I also think it offers Halo game play that many people enjoyed historically... static sets. H2 on most maps, was best played from a static set - you controlled points on the map as a team and movement was mostly to and from those spots in a constant attack/defend tug of war. In H3, Reach, and H4 maps increasingly reward moving as a team with constant aggression. After H2, spawns are forced until they move, and a team must move together to keep the other team on spawn after the base area moves. (general statement)
People that are not highly skilled have trouble with that, as do people that are locked into a play style and cannot change. I also think people love to just "dong" and hate getting "donged on", so you get very polar reactions to maps like Isolation and Settler. Those who play with groups who know what to do, set up, lock people down, and don't let the other team breathe... those who don't, have it done to them in unequal skill matches.
I definitely think there should not be a power weapon in power positions. The positions are all the incentive people need to be there. Power weapons should be elsewhere as an incentive for teams set in the power position to move, and as an option for folks on spawn to attack the power position if they gain control.
Take the rail gun off the hill and place something mid map, or place an opposing power weapon that makes sense in the building on the open side of the map. Better yet, move the rail gun off the ridge to the middle and place a snipe in each base on a static spawn.