35-180 is the 10½" reel. The 35-90 is the 7" reel.
Whether the 35-90 or 35-90B or the 35-180 or 15-180B,
1) the standard tape many machines were set up for from the factory
2) one of the better tapes back in the day
3) a quality product that is readily available NOS
4) a product that has never been listed on any of the sites that mention problems with tape. this consistent quality even today means buying NOS one will know what they are getting and it will work as they expect.
There is not much that can be said bad about it, it just works and works right.
Yes there is better but that is new production and sells for new tape prices.