Got to be the monster as it's derived from the 851 super bike so has all the right geometry & is more adjustable than the SS, as for weight there's bugger all in it,
more good bit's around for the monster as lots of parts from 748/9** models fit.
Just my opinion others will say the SS is better & to be honest I think they both work well for the power a DD bike can produce.
I have built DD bikes from both

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