No better place to make my first post on this forum! I've owned an 05, 12, and 15 Tacoma and currently own a 16 4Runner. Regardless of specifications listed, the rear passenger area of the 4Runner feels several inches larger than that of the Tacoma. In fact, I traded my 15 Tacoma in on the 4Runner because a rear facing car seat would not fit in the Tacoma and leave enough room for a front seat passenger. The exact same car seat fits in the 4Runner with zero issues.
Beyond that, the new 3.5 engine in the Tacoma is causing all kinds of drive ability complaints due to its low rpm torque, or lack thereof. Just google 2016 Tacoma transmission and you'll see tons of complaints. Better yet, go drive one and pay attention to low speed parking lot on/off throttle situations and highway passing situations. The engine just isn't going to work in this truck, they are going to have to address its lack of performance.
The 4Runner is still using the 4.0L engine that has been around forever. Loud and low on power, but bulletproof and works well.
Having owned both, the 4Runner is hands down my choice.