I would say that the GTI will offer more practicality than the other options on this list, but it will neither be smaller nor more tossable than any of the others. The GTI is a fun to drive car, this is true, but the MKVII will be larger than the current car, though it will be engineered to be lighter weight by supposedly as much as 200 lbs, it will still be a relatively heavy car compared to something like the next generation Miata, which Mazda promises will lose weight and decrease in size compared to the current Miata.
If you need more practicality, the GTI would be my choice. Rumors are that the next MKVII GTI will be lighter than the current car, larger, more powerful, and more refined. Top Gear posted a more comprehensive list of predicted changes on their website, but that's the basic rundown. If you get the four door model, you can easily seat four people comfortably plus cargo, make runs to Ikea, and move a surprisingly large amount of stuff for the car's size. Doing the same in, say, a Miata will be decidedly more challenging. As a trade-off, the Miata will offer a lot more rear-wheel drive bang for the buck open top fun.
I dare say most people will say most of these cars are not direct competitors to the GTI or to each other, but people sometimes cross shop based on what factors beyond the obvious. For my money, the GTI is the car that is both fun to drive and exceptionally practical in everyday use. If that's what you need, then I would seriously consider if. If you can sacrifice the practicality, never need to drive anyone other than yourself, have no use for things like cargo room or rear passengers, get a BRZ or Miata.
Just my two cents.