Spider climb doesn't say how your base climb is affected, so I’m confused. Does it stack, does the larger amount override the smaller, or does spider climb just overwrite it, period? For example a summoner's eidolon with the Climb and Major Spells evolutions, or the summoner himself with the Climb evolution that has his wizard friend cast spider climb on him. Not sure if that classifies as an ability and thus excluded from your options.
The subject can climb and travel on vertical surfaces or even traverse ceilings as well as a spider does. The affected creature must have its hands free to climb in this manner. The subject gains a climb speed of 20 feet and a +8 racial bonus on Climb skill checks; furthermore, it need not make Climb checks to traverse a vertical or horizontal surface (even upside down). A spider climbing creature retains its Dexterity bonus to Armor Class (if any) while climbing, and opponents get no special bonus to their attacks against it. It cannot, however, use the run action while climbing.