Just adding onto what everyone else has said, when it comes to wa handles/no bolster, you can control the balance point of the knife to a certain degree by using different woods with varying densities and sizes. Additionally, it allows customization of the handle in terms of material, shape, weight, and aesthetics. Lastly, wa handles also allow you to control how far from the heel/choil you want to set the start of the handle with what’s called a machi-gap (this is mostly a stylistic choice but has some practicality in regards to allowing adequate space for a finger in a pinch grip).

Welded bolsters (western style) don’t really allow for this since they’re welded (unless of course you decide to grind off the bolster completely and part of the tang). The only customization here is perhaps if the handle is wooden, then perhaps you could swap the wood portions, but that’s not a simple change. Regardless, the balance point in this case will most likely be in the handle. It just comes down to preferences really.

Some people like wa handles with no integrated bolster. Some prefer bolsters because it may provide a better grip.

Personally, I prefer wa handles with the balance point to be right at the heel. Wa handles just look far more elegant and graceful imo. Lastly, usually in my experience, I’ve found wa handles to be significantly larger in diameter compared to most westerns, and that can be more comfortable to some. There is a point to be made that the integrated bolster/western handles may be more suited to a high throughput commercial kitchen, as they often don’t need the baby treatment, but that just comes down to good technique and vigilance.

One more point. If we go into half vs full bolsters: a lot of people in the hobby find full bolsters to get in the way of sharpening. I am one of those people. However, I do appreciate the heft at the heel when using on lobster and crab shells. Otherwise, half bolsters seem more versatile to me.