The ergonomics of the push handles of the Pfeil tools fit my hand better and give me better control than the Flex Cut. I find myself using the small tools MUCH more than the larger ones. And the Pfeils seem to come in a wider variety of sizes, especially on the smaller end, and those get the majority of the use. It's easier to control your cut by taking 3-4 passes than it is to take 1 big one you drive with a mallet. But for the bigger job of stock profiling the mallet driven tools have their place. That said, I still use a rasp more for that, as, it is less likely to induce a grain split or tear-out.
What ever you do, learning how to sharpen your tools is one of the most important elements of good carving. So I use a leather strop a lot.