Best low budget area to stay in Tokyo?

Hi everyone. Flying to Japan next month, and I'm still trying to decide my accommodation for a week in Tokyo,. I have two bookings and need to cancel one, but I'm divided between:

– Sumida area, hostel near the Asakusa metro station

– Otsuka area, hostel close to the Yamanote train

Both are around 500€ for a 6-night staying and our budget doesn't allow us to choose a more central (but pricier) area. Which area do you think it's best? Or both are bad options?

Second, would you recommend getting the Tokyo Subway Ticket (72h) or should I go for the Welcome Suica Card? Reading mix reviews.

Thank you fellow travelers!

by Dani_blah