Absorbency:

Natural Bristles: Natural bristles can absorb oil and distribute it along the length of the hair shaft. This can help to add shine to the hair, improve texture, and reduce oiliness at the scalp.

Synthetic Bristles: Synthetic bristles do not have the same capacity for oil absorption. This can lead to a build-up of oils at the scalp, making hair look greasier faster.

Usage: 

Natural Bristles: Best used on dry hair, as wet hair can weaken the bristles and shorten their lifespan. They're especially great for finishing brushes or for styles that require a soft, smooth look.

Synthetic Bristles: These are more versatile and can be used on both wet and dry hair. They can detangle and style hair, and are less likely to cause breakage when used on wet hair.

Maintenance:

Natural Bristles: These require more care and upkeep. They should be washed regularly with a gentle shampoo to remove oil and product buildup, and should be replaced more often as they can wear out faster.

Synthetic Bristles: These are easier to maintain. They can be washed less frequently and are generally more durable, meaning they will need to be replaced less often.

In conclusion, both types of bristles have their advantages and disadvantages. The right choice for you will depend on your hair type, your styling needs, and your budget. Be sure to do thorough research before purchasing a hairbrush, and don't hesitate to seek advice from hair professionals.