Stay closer to Yamanote line or Marunouchi line in Tokyo-I can’t decide! Please help!

I have two accommodations booked in Tokyo and can't decide. Both are very similar in terms of amenities (although one is slightly cheaper).

One is located in Takadanobaba-six minutes walk from Takadanobaba Station on the Yamanote Line.

The other is located in southern Nakano City, just a few blocks from Oiwake Park and six minutes walk from Shin-nakano Station on the Marunouchi Line.

One of us is coming from Haneda, one from Narita.

While in Tokyo we plan on visiting the Nakano Broadway flea market, Gotkuji Temple, Ghibli Museum, Shimo-Kitazawa and TeamLabs Borderless MORI building. Plus a little Shinjuku and Shibuya. (it's not our first Tokyo visit)

When leaving Tokyo, we will be traveling to Nagano.

Both places seem to have similar travel times to the locations we want to visit, but I know nothing about either neighborhood, or which line is better to get around on. I would love some input from anyone who can help me decide! Thank you in advance!

Edit: Thank you to everyone who provided helpful responses. Sounds like Takadanobaba is a better fit for our trip. You helped immensely!

by RainyDayRabbitHoles