I agree, he can get an advantage over his droid 'army' however. But that's just it, it isn't an 'army' as such, the Wookieepedia title is misleading, he had a bunch of droids defending his ship - say 50 or so. And had a bunch of 'informants' if you like on Nar Shardaa, but were not talking a military grade armarda or anything. He does have a HK-51 factory though. But the point is, G0-T0 would strike from the shadows.
Also HK-50s weren't brainless morons like the Trade Federation's poor excuse for Droid Soldiers... Seriously, G0-T0's spy network was Galaxy-wide, he wasn't simply limited to Nar Shaddaa, and his base of operations was mobile, so that also makes it hard for Plagueis to take on G0-T0.
Fact of the matter is neither one has a fixed base of operations, so it comes down to who would be better able to find a needle in a haystack when the needle is moving, and the answer would likely be G0-T0.