Been running the Speed-Feed 450 and 350 heads with the Echo .095 line for the past 5 years and have no complaints. So far the easiest loading heads we've used, I know they'll be a couple guys who will chime in and say how hard they are to load, that hasn't been my experience at all with the speed feed heads. Haven't tried the Husqvarna head yet, might look into it.
What I like about the Speed-Feed head, apart for the easy loading, is the nice big flat bottom that glides right over our St Augustine grasses with little effort. Every head we've used with the "button" on the bottom gets hung up in the runners.