I know it sounds ridiculous, but I've seen enough of these things that I can typically tell just at first glance. Factors in play here are tentacle spacing (you can see the haddoni's are more closely packed than the suspected gigs), tentacle length (the haddoni's are stubbier), fold patterns (the suspected gigs have deeper, more pronounced folds), mouth color (the haddoni has a deeper reddish rim around its mouth - I've never observed that on a gig), and overall color (haddoni blue is essentially solid blue throughout - even the bluest gigs are tan at the base of the oral disk and tentacles, with blue tips). Although I cannot be 100% positive on ID without seeing the feet and stressed/acclimating gigs and haddonis can be deceptive, the above factors make me fairly confident here.