Both designs are used to suppress stray light inside the hood. In general, a flocked/felt-like lining is likely better at absorbing light than plain textured plastic. However, the textured 'sawtooth' interior is widely used and appears to work well in practice.

Based on the community answers, even higher-end modern Canon RF lens hoods now use the textured interior rather than the older felt-like lining, which strongly suggests Canon considers it sufficiently effective. A practical advantage is that textured plastic is less prone to holding dust and is easier to clean.

So the best summary is: flocking may be slightly better in theory for light absorption, but textured hoods are acceptable and generally not known to cause image-quality problems in normal use. The difference is likely minor compared with simply using a properly designed hood in the first place.