Here is my analysis of the three:
FM258 - this is my top choice due to the iterations that have been coming out for the last year. The slight tweaks to add the 12x148, the XL size, the SL option, shows that the people doing the layup are confident enough to expand the product offering. I also like this suspension design due to the copy of the Spark.
CS-M06 - this is my second choice due to the large number of builds and the iterations off of the CS-M36. They also have been doing the XL for quite some time and my order won't be the first run. I also like this suspension design because it is tried and true.
M-145 - I like the idea of this frame, the slackness, the full active rear triangle, but I wish it was squishier. 120mm front/rear would be unique and something we all have been wanting; a trail bike from the OEM for under $1000 (with shock). They are also on their first run of frames and I don't want my $$$ to be the revenue that drives iterations.