Both have good Omega 3 EFA.
The oil form is a bit more concentrated but since it's an oil it also loses some of the other vitamins and minerals in the extraction process (with the exception of vit E) as well as the lignans and fiber which the ground flax contains.
If you use the GSG ground flax it is also a sprouted seed so it stabilizes the EFA in the seed which increases the conversion efficiency of the EFA's for better bioavailability and also prevents rancidity which the oil and regular ground flax are prone to.