The morphology and compositional uniformity of strained alloy films have recently been predicted to depend on the sign of the misfit strain between the film and the substrate. Other theories have been proposed where this is not the case. In order to test these contradictory predictions, we deposited In0.26Ga0.74As films on GaAs(001) and InP(001) substrates by molecular beam epitaxy. This alloy concentration was selected because its lattice parameter at the growth temperature (5.77 Angstrom) lies directly between those of GaAs (5.67 Angstrom) and InP (5.88 Angstrom). This enables growth under both 1.85% compressive and tensile misfit for the same film material. The surface energy, surface diffusivity, elastic parameters, and thermodynamic coefficients are nominally identical. This leaves the sign of the misfit and the film-substrate interface as the only variables, and the latter is expected to be a minor contributor. We find that the films grown under tension develop much smaller perturbations than do the films grown under compression.