No matter which 2013 Golf or GTI you choose, you end up with an interior that offers the same amount of space and usability--and nearly the same amount of comfort and refinement. The Golf, even in its base form, includes good front seats and has a pervasive feel of quality throughout the cabin. But compared to other small-car models, it lacks backseat space--especially in three-door models.
Considering the Golf's boxy look, it's a bit surprising that it's not more spacious inside, in terms of back-seat and cargo space. Three-door models feel especially tight in that entry to the back is difficult, but in both models there's limited legroom--not nearly as much as in other compacts like the Kia Forte or Ford Focus, to the point that some adults will have trouble fitting. On the other hand, headroom is quite good, and the rear seats do have adjustable headrests and an armrest. Rear seats also fold down nearly flat to expand cargo space.
In front, it's a different story. The 2013 Golf and GTI have some of the best accommodations for the driver and passenger, of any affordable small-car models, with supportive, adjustable front seats (although the seat adjustments can be a bit hard to reach). The seats themselves are shaped well for most body types and sizes, and they're firm for comfort over long-distance drivers.
Volkswagen puts high-quality materials in the Golf's cabin. Visibility is good, too, but the base of the windshield is rather high, the result of European pedestrian collision standards.
Overall, refinement and ride are excellent across the model line for both Golf and GTI models. Only with the Golf R do you get a ride that's somewhat harsher--as well as a little more engine noise.