I haven’t seen tests comparing the different temps with the SST40. This emitter is basically an improved XM-L and behaves like other LED’s, so yes, 6500K will likely produce more lumens than 5000K, but the difference shouldn’t be dramatic.

I have a 5000K FT03 and I like it, but you should choose the 6500K if you want the most reach possible. Color temperature really isn’t terribly important on a dedicated thrower, IMO. I was worried about weird halos and an uneven corona, but I’m quite happy with the tint on my Neutral White FT03.

I imagine that the 5700K is a good compromise, though I don’t think we’ve seen beam shots from that tint.