Hey Izak
The waterproof rating on a jacket does not necessarily state truly how waterproof such a jacket is, it is a claim by the manufacturer and should be taken with a grain of salt. The reason being is that there is no standardized test in use as of yet. The jackets are either sent to labs for testing or tested in house, therefore testing methods vary. For instance, some manufacturers add pressure to simulate windy conditions with pelting rain, where others don’t ect.
So its wise to rather look at the material used in the Jacket. I cant find what the Mac in a sac is made of and therefore cant comment on the material waterproof capabilities. The FA Hurricane is made of VapourTex , which is fairly waterproof. However no matter what material used, it well get soaked at some stage.
With regards to durabilty, it depends what you want to use the jacket for. Will it be a “just incase” jacket or a go to for rainy days ? I presume the mac in a sack is a 2.5Layer jacket at best (hence the weight and packability). The FA is a 3layer jacket and will fair better during some bundu bashing and the shoulder coverings will stand up to pack abrasion.
No matter how breathable a jacket is claiming to be, I would still opt for one with ventilation options, such as the pit zips on the FA. It just helps dump heat when you are slogging up a hill in humid wet valleys ect. Cause a waterproof jacket defeats it purpose if you get soaked from the inside.
Also taped seams are a necessity, this prevents the water seeping through the micro holes made by the jacket stitching.
I don’t have personal experience with either of the jackets but would opt for a more durable jacket with ventilation options such as the FA.