put very simply, you end up landing faster at the higher airfield.
Whilst completely true, this answers a question which Doors to Automatic did not ask. His question was:
What difference does that [an airfield being at 2,500' as opposed to MSL] make to braking capability?
I would think the answer is not much difference to braking by the wheels, though any aerodynamic braking would be reduced. This would probably have only a marginal overall effect on the braking, on a like for like speed basis.
Of course, this ignores aquaplaning, which could also be affected by density altitude. Not knowing of any effect this might have, my first hunch would be that the relatively greater tyre pressure compared to the ambient might even reduce the speed at which aquaplaning occurs, thus helping to reduce stopping distance.
Anyone with greater knowledge and FACTS care to enlighten us?
PM