I own the full range of Festool drills as well as most of Milwaukee's and a couple of Hiltis as well. In general, I would say if you're looking for value-for-money, the Milwaukee drills are hard to beat: they have excellent torque and speed for their size, weight and cost.
If money is less of a concern and you just want the best, the Festool drills are a joy to use due to their extremely sensitive trigger control, precise clutches and thoughtful little additions like the built-in magnetic bit and screw storage and the quick-change chuck system. Also, the PDC in particular is the highest speed cordless drill on the market, with a blistering 3800 RPM in fourth gear that will make quick work of soft materials and absolutely demolishes concrete when using the percussion-drill functionality.
Where the Festool drills all suffer (besides price) is in torque. The PDC is the highest-torque drill Festool currently has available in North America, and it comes in at just over half of the peak torque of the current Milwaukee M18 Fuel model and about 60% less than Hilti's flagship SF10W-A22. The TPC model that was just released in Europe claims to boost a 40% torque improvement over the PDC, which will close some of the gap, but the fact remains that it will still lag other high-performance drills by quite a lot in this area.
If you regularly find yourself using large auger, spade or Forstner bits, it might be a good idea to pass on the Festool line and look at alternatives. Hilti's drills, in particular, offer similar fine trigger control and excellent craftsmanship while also packing a lot more power. But they're even more expensive than Festool, while being larger, heavier and very conventional in design, lacking those extra functional touches I mentioned earlier.
There's no one perfect drill out there that I've ever found, just a lot of good models that make different compromises and trade-offs. But if you cut me down to just one, I'd probably go with the PDC, because it's got extreme versatility while having performance that's good enough for most work even if not the best.
