Profiled by Ken Carman
I believe I may have Foreign Extra in Montreal a long 
time ago. But so long ago: hard to be certain. Wiki does not have it currently being sold in Canada, but hey… twas way back in the American beer dark ages: the early 70s.
Both decent head, the Foreign seems to have a little more depending upon the pour. So… probably about the same. The Extra is obsidian with a few vague garnet highlights. Foreign is just obsidian.
Aroma on the Extra is a little soured, as expected due to Guinness addition of a bit of soured beer. Deep grain sense that could be mistaken at first for a lot of Black Patent roast, but more very roasted barley sense.
The Foreign has almost a slight phenolic sense, and little to no soured: just malt and roasted barley… more than the Extra.
Mouthfeel: the Extra… foamy carbonation tingle and deep roast. Foreign: alcohol higher, smoky… peated malt perhaps? Can you “peat” roasted barley? I would think so. Less foamy carb.
Taste: the Extra seems lighter and, again, a bit soured. The Foreign is impressively malty and roasted barley-ish. So much more complex. As it warms you do get more “soured” sense, but the malt.roasted barley mix dominates. Both have about the dame level hopping, which obviously means more hops in the Foreign, otherwise that would seem less hoppy due to body/abv jump.
Overall, as much as I like Extra, Foreign is just so much more to enjoy: Guinness on steroids. I recommend both, but prefer the Foreign: only cause as I have said so many times, “I have taste buds that need beating.”