Depends on the context but in most cases these are a convenience, syntactic sugar.

Take SendOrderToVendor::dispatch($order)->onQueue('orders'), for example.

This could also be written as:

$job = new SendOrderToVendor($order);

$job->dispatchOn('orders');

(Exact function calls may not be correct, I'm on my phone)

Functionally identical - same code path. The main gain is ergonomics, but it's entirely your choice how you prefer to write this code.