the basic in modular synthesis is... freedom....
you dont have to stick to osc-filter-amp
well you do in someway
but you dont have to
you can use lfos as sound generators and such
basicly you can build what ever synth you desire...
the g2 it does offer much more then the nord lead series but consider that if you want instent sounds,modulars are not realy for you
because they need to be patched which takes a bit more time then programing a simple atrcitecture synth...
if you do want a modular synth and its for studio use only consider the creamware pulser 2 dsp card aswell
the modular 3 is even more powerful then the clavia ones and it offers many methods like granular synthesis for instence that the nm doesnt offer but it doesnt have pysical modeling modules...