Pros and cons of grip/handles materials

Bone is supposed to provide a good grip when wet. Ivory is probably similar.

Horn is OK when wet, and a good tough shock-absorbent grip.

Antler is supposed to be somewhere between bone and horn.

Wood depends a lot on the type of wood. Some wood will be slippery when wet, some wood will be fragile and liable to split. Wood is easy to get, and easy to carve. If the wood is reinforced by ferrules etc (e.g., fuchi and kashira), and the shape of the grip assists gripping (as on lots of wooden Indonesian and Philippine grips), then slipperiness and fragility become much less of a problem. But there's a reason why wooden grips are often covered/wrapped, while bone, horn, and antler grips are left naked.

Bare metal is more slippery than wood, but stronger. I'd avoid bare metal unless the grip is shaped for a secure grip, e.g., disk pommels on tulwars, or other similar features to prevent slipping, such as widening towards the pommel.

A leather-covered grip should be less slippery than bare wood when wet. Ray skin (or shark skin, or other fish skin) provides a very secure grip, wet or dry. Can be uncomfortable with bare hands due to roughness, depending on the skin and treatment. (Use gloves if needed.)

Wire and cord wraps provide a lot of support for a wooden grip core, and (if done properly) greatly reduce the chances of the grip core splitting. Both wire and cord can be uncomfortable with bare hands. Use gloves if needed. Another solution is to cover the cord wrapping with leather. A cord wrapping provides a good secure non-slip grip. A wire wrap can do the same, or can be a lot smoother and less secure, depending on how it's done. Twisted wire wraps are more secure.

Flat cord or fabric (Japanese-style ito, many Chinese grip wraps) provides less grip than round cord. Wrap styles with overlaps, twists, or other features to provide more texture (e.g., menuki under the wrap) provide more grip.

Cord and fabric wraps can get dirty and be hard to clean. Wire wraps can rust (if iron or steel). Bone and wood (and horn to a lesser extent) can crack. Bone is often used as slabs on the sides of a full-width tang, and cracks are not an immediate problem. Bare iron can rust. The surface of leather can be damaged. The lowest maintenance grips are solid metal and horn. Antler and wood are next. In my experience, dirt shows more on bone.

Appearance is in the eye of the beholder, so the best grip for appearance is what you like best. But I can say a little more. Often, what's done with the grip material is more important than what the grip material is. One can have ugly bone grips, beautiful bone grips, beautiful plain grips, ugly plain grips, beautiful carved grips, ugly carved grips. I've yet to see a beautiful cord-wrapped grip, and I find wire-wrapped grips to be on the ugly side on average.

Some modern materials - especially synthetic rubbers - can work very well. Comfortable, secure when wet, shock absorbent. Not very good for historical appearance on historical swords.

Great explanation, thanks for sharing.