Arguably the most important benefit of 27.5 over 29 is quicker acceleration. This is the "snap" that a rider feels when they push hard on the pedals. It is affected not just by overall static weight but also where the weight is distributed throughout the wheel. The farther the weight is from the center of the hub, the slower the acceleration. So a similarly constructed 1000-gram 29-inch wheel is slower to accelerate than a 1000-gram 26-inch wheel—because the larger diameter rim and longer spokes place weight farther from the hub. The key to snappy acceleration is minimizing the weight of the outermost components (rim, nipples, spokes, tire, tube). As you can see, a 27.5-inch wheel is only 1.5% slower to accelerate than a similarly constructed 26-inch wheel, but a 29-inch wheel is 3.6% slower than a similarly constructed 26-inch wheel.
A larger tire contact patch, increased stiffness, and optimized frame geometry improve traction, braking and handling.
The larger the diameter of a wheel, the greater the contact patch of the tire. A larger contact patch results in better traction, which leads to improved acceleration, deceleration and cornering. As you can see, a 27.5-inch wheel has a similar contact patch to the 29.
Lateral (side-to-side) frame stiffness can be affected by wheel size. To accommodate larger wheels, frame dimensions must be elongated. Therefore, a size medium 29-inch wheel frame has more lateral flex (bottom bracket and head tube) than a size medium 27.5 or 26-inch wheel frame-set. Additional flex compromises handling under heavy pedaling or sharp cornering.
The larger the wheel, the more difficult it is to optimize geometry, especially on smaller frames. As the frame size decreases, headtube heights become higher (in relation to saddle height). On 26 or 27.5-inch frames, it's less of a problem, but geometry limitations can affect smaller 29-inch-wheel frames.
Check the ranges of 27.5 2015 Model Giant Talon Bikes - 2014 - Giant Talon 27.5 Line Up