I also like Warren knives for starting out for this reason: You need to keep fixed handle knives honed and sharp and newbies oft time ruin a good knife because they do not know how to keep it sharp. The Warren system of disposible blades at least allows the new carver to have a sharp knife for around a buck a blade. Plus they can have a variety of blade shapes including handle for around $20 to see what shapes they like and fits their carving needs. A good fixed handle knife can get pricey so it's important to know how to take care of it.
I certainly am not against a good fixed handle knife and Knotts, Lyons, Flex cut, etc. all make quality knives and if you purchase from one of these company's you will be very happy. I personally love Cape Forge knives and have used several shapes for years. I also have one from Diobsud Forge that is my favorite but they are out of business at last check. BTW, I still use Warren blades and gouges for some tasks.
In a nutshell I like Warren for entry level and then move up as you gain knowlege and skills.
Willy