Obito and Madara = Uchiha + Senju
Sasuke = Uchiha + Hagoromo's Yin + Senju? (If Kabuto gave Sasuke Hashi's DNA while unconcious)
Those 3 no longer only wield Uchiha power but have Senju power as well. Not sure about Sasuke though he has power from Hagoromo who technically is Indra+Ashura. Them inheriting his power. Though Sasuke doesn't actually use Senju power. Rinnegan is something that's acquired through both Indraand Ashura but is still it's own seperate power. That being Hagoromo's.
If your question is who has the strongest descendants, then it would clearly be Uchiha. Though he strongest 3 wield additional power besides only that of an Uchiha (Rinnegan/Senju), they are still Indra's descendants, not Ashura's.
If you are talking about only pure Uchiha or Senju power, then it's a bit trickier. Shisui has KA though it's only once a decade (or twice if it's one use per eye), Obito with both eyes and without Senju DNA still would be a force to reckon with (Kakashi doesn't have Senju DNA and isn't an Uchiha yet he improved in Kamui's use and was able to use it more times before being depleted). In Obito's case, he'd still grow blind in time but for most opponents, it uld still take one snipe to deal with since most wouldn't react.
Sasuke still has his legged Susanoo with Blaze Release while Itachi has Totsuka and Yata and is also skillful and has battle smarts.
In the past (Madara and Hashirama's time), Senju were the strongest. Madara and Izuna were the only noticed ones in the Uchiha and Hashi and Tobirama the only ones in the Senju. Hashirama and Tobirama being superior to them either way. EMS Madara by himself still being inferior to Hashirama. Still no other noticeable Uchiha and no Senju besides Tobirama (Senju still suoerior).
Though if DMS Obito, Itachi, Shisui, and EMS Sasuke would've lived during their period, I do believe things would've been different. Tsunade is the only other Senju who I've heard of that isn't like the rest.
There were probably other Uchihas and Senju who stood out from the rest (Indra and Ashura's transmigrants especially) but unfortunately, we haven't heard of them.
I'll go with Indra's descendants in general.