etek 2: poppet gat so more kick, louder, more air efficient and easier to maintain. you also have great tech support from planet
dm8: spooly gat so very smooth to shoot, quiet, less air efficient and requires a bit more attention and time for maintenance. you also have great tech support from dye
thats the main differences
apart from that its your own personal choice of what you like. they are both completely different to shoot and feel very different in the hand.
so if oyu can try them out first then decide what you want