In built-up areas to accuracy varies between the units, (the 60CSx without it will take slightly longing to get the same accuracy as the other 60CSx) but as soon as there's open sky overhead the 60CSx with the external antenna gives better accuracy again. There are occasions when the 60CSx without it showed better accuracy but only for 1-2 sec. The 60CS was hopeless even with an external antenna.
Below are the tracks of all 3 along the tall buildings in Robinson Road. In my opinion, the 60CSx without antenna faired the best as it tried its best to track me going around Hong Leong Building. While the 60CSx with antenna had a hard time with multi-path signals. In open areas like the ECP all three were on par. (click image to see more)