If you need/want speed, stick with 5k MH. If the Starlight could shoot 2up it would be more of a contender to replace MH in the speed category but still slower. Or you could buy two or more Starlights....
In any case this discussion of speed isn't a knock on the Starlight, my understanding is it was not designed for speed. The main benefit we see is lower power consumption and small footprint.
You can actually get a 7s expo time with HVP, with glass and film, with a good 5kw positioned to shoot 1up.
But even with DTS those super fast times with the Starlight are either extremely fast shooting emulsions or people just aren't fully exposing, which is fine for some all plastisol shops, no go for the rest of us. When some manufacturer matches an emulsion to the Starlight's LED spectral output the times have the potential to get quite fast.
M&R will test your emulsion for you. Give them a call. They emulated one of our screens- same mesh, emulsion, amount of diazo, right down to the same scoop coater I believe so we could double check the times against each other.