I'd choose Uchiha, the clan with the highest potential and the coolest and most OP powers.
2. Perfect Susanoo is reason enough to pick EMS i.e. Uchiha. Everything else is just a bonus. Plus, there are more chances of obtaining cool and badass jutsus when you're in the Uchiha clan.
3. The powerful chakra and stamina of Uchihas keep on increasing as time progresses, to a point where further increase is no longer required. Did you see EMS Madara? His chakra reserves were immense. He easily had enough chakra to learn Sage Mode. On top of potentially learning SM, he could learn FTG, Edo Tensei etc adding that to the usual Uchiha stuff like Sharingan, MS, PS, meteors, Kurama summoning, he had the potential to do pretty much anything. Not so much with Hashirama or Senjus in general. Hashirama and Tobirama couldn't gain Sharingan and other Uchiha powers, but Madara COULD get Sage Mode over time (Hashirama), and even learn FTG (Tobirama). That's what I mean by Uchiha's potential, and that's why Uchiha is the best clan to be born in. You have or can have by time the best of everything.
1. Choosing Senju because of Tobirama isn't the best decision, because an Uchiha can do whatever Tobirama can do, and more.If I could make my own moveset and be at least Tobirama if not Hashirama/Madara level, I'd pick Senju. If I could get EMS as an Uchiha it would be tempting, but the only Mangekyo that impresses me truly is Kamui. If I could completely design the EMS STJ I'd be tied with Uchiha.
I like health & stamina tanks that take forever to kill or wear down.
2. Perfect Susanoo is reason enough to pick EMS i.e. Uchiha. Everything else is just a bonus. Plus, there are more chances of obtaining cool and badass jutsus when you're in the Uchiha clan.
3. The powerful chakra and stamina of Uchihas keep on increasing as time progresses, to a point where further increase is no longer required. Did you see EMS Madara? His chakra reserves were immense. He easily had enough chakra to learn Sage Mode. On top of potentially learning SM, he could learn FTG, Edo Tensei etc adding that to the usual Uchiha stuff like Sharingan, MS, PS, meteors, Kurama summoning, he had the potential to do pretty much anything. Not so much with Hashirama or Senjus in general. Hashirama and Tobirama couldn't gain Sharingan and other Uchiha powers, but Madara COULD get Sage Mode over time (Hashirama), and even learn FTG (Tobirama). That's what I mean by Uchiha's potential, and that's why Uchiha is the best clan to be born in. You have or can have by time the best of everything.