Whether it makes wood more brittle is a hard one since brittle fracture isn't a normal failure mode for a knife handle. Stabilised handles don't crack from brittle fracture any more than non-stabilised do. Now if you were talking about pool cues you might have apoint, but since they also use stabilised wood for those without too many problems, I think its probably a moot point
More important, you can take a wood that would otherwise be too soft and too weak and by sabilising it you can make it a good handle material. Many of the burrs, and spalted woods fall into this category.
The resin is generally some type pf acrylic monomer which penetrates easily into the wood under the alternate effects of a vaccum followed by positive pressure. The wood is then cured in an oven where the resin polymerises.
There are advantages and disadvantages. On the plus side you can get stunning grain patterns, good stability, durability, and consistent machinability. It is also easy to finish, merely requiring fine sanding to your chosen grit. The "finish" cannot be sanded through as can happen with a superglue finish, or some oil finishes.
The downsides are cost, which is a lot higher than for untreated wood, size, the blocks tend to come in standard sizes which may or may not suit your particular project, weight, if you want a light knife then you will save weight by using unstabilised wood and giving it an oil finish, smell, filing and sanding, never mind using power tools is like working plastic, it stinks, and finally, the finish can look more plastic like than some people want.
For your first few knives I always advise people not to spend their money on expensive wood, or at least, not the stabilised version of the expensive wood. Irrespective of how supporting folk are to a new makers first knives, most have a lot of faults ranging from poor design to poor heat treating and questionable fit and finish. I just think it a shame to spend a lot on the materials unless you know that you will be getting the most from them. Also, I find there is a lot more statisfaction to be had from getting a good finish on natural wood than there is from buffing up something which is plastic impregnated. I do use stabilised wood, but with the exception of how easy the finishing is, its not as much fun as using untreated wood.
