Under generic circumstances, Kasich would probably be a stronger candidate than O'Malley (Swing State Governor with congressional experience/ television background VS Mayor/ Governor from safe Democratic state.)
Booker would help O'Malley with young progressives and African Americans.
Martinez adds diversity and can be a strong surrogate in the West.
The default map would probably favor Kasich.
Kasich/ Martinez- 292 Electoral Votes
O'Malley/ Booker- 246 Electoral Votes
If it's a strong environment for Republicans, Kasich could also carry New Mexico, Virginia and softer Midwestern states.
If it's a strong environment for Democrats, O'Malley might keep Colorado, Pennsylvania, New Hampshire and Iowa from swinging to Republicans.