Madara would be around Old Hiruzen level at best. They would be more or less the Sarutobi clan with a couple lil quirks.
No it more like uchiha is more potent than the average ninja but senju have more chakra and staminaEven so the Uchiha are stronger in ninjutsu regardless. What I mean is if an elite Uchiha were to use Water Style and a an elite Senju used Water Style, the Uchiha's would be much more damaging.
On the opposite spectrum, even though the Uchiha have more potent chakra the Senju can take far more damage due to their high endurance. So they can take what the Uchiha can dish out.