^I suppose a combo is the best. Can't imagine a meth+H 'semi-speedball', which just has to be godlike. I know a H+C speedball is pretty damn amazing.
But, on the other hand, an opiate high on its own is just so damn relaxing and blissful that I think I might enjoy it even more actually. Granted, the rush of the formerly mentioned combos are the most enjoyable feelings I can imagine. But I really like just being super relaxed and chill as well, which isn't exactly how I'd describe the feeling of a speedball. So it's a little hard for me to decide which I like the best. If I can only pick uppers OR downers I'll always choose downers though, that's for damn sure.