Losi 8ight t 2.0 Brushless help

I bought a Losi 8ight t 2.0 to convert to brushless for a new 1/8th scale track that has been built near me.
I have had a good read on the forum & I must say it has been fantastic help - Great site :
The combo I have narrowed it down to, is the Mamba monster or the Tekin rx8.
Would I be right in saying that for longer runtimes I would be better with a low Kv motor & run 6s lipos?
Im really not sure what I should buy so was hoping I could get some advice on a good combo to use.
I read that the tekin motors had some problems but have now been sorted.
Thanks in advance