If you are particularly looking to load-balance http traffic, then an http-specific load balance (like Pound) is going to be more flexible than a generic TCP load balance (like ipvs, or balanceng). An http load balance can make decisions based on http headers, which can be particularly useful in linking client cookies to a particular backend.
Note that in addition to the products you've listed, Apache can also act as a load balancer. Additionally, there are a number of tools that can act as a "reverse" caching proxy in front of your web servers; these tools can all perform load balancing and can substantially increase your performance if content can be served from cache. Varnish and nginx are both popular choices for this purpose, and Apache can also act as a caching proxy.