I use a ferriers rasp a lot . They work real well for parliamentary shaping .
As was said , they take a lot of wood off quick . I have never had a sharp one tear the wood . However I also pay attention to grain and rasp with the grain not against it .
Good Ferrier rasps should also have 2 sides . A course and a fine.
The fine side being courser then a cabinet rasp.
Use the finer side for clean up then progress to a smaller rasp , then files and scrapers .
On softer woods like English walnut or red or big leaf maple , I shape using my older Ferrier rasps that have began to get on the dull side .
In fact I have a couple which were give to me because the were getting to dull to use for shoeing ..
If your building from a precarve , I would not use one . But if your staring from a plank and working the wood down to a general shape , then they work wonderfully IMO