The 166 is definitely more special. The GT is a dime a dozen compared to the 166.
They made fewer than 100 000 of the 166, and a 3.0 Sportronic is a rare beast indeed - fewer than 200 ever sold in the UK, with fewer than 40 of those being pre-facelift.
The 3.2 GT is a lot more common compared to that, with about 500 brought to the UK out of the nearly 4500 produced.
Unfortunately value seldom has anything to do with rarity, more often it's to do with looks and how good the car's perceived to be. For instance I owned a Bond Equipe GT 2+2, one of only 4 still running. But nobody knew what the hell it was despite it looking like a mini Aston Martin, so it was worth slightly less than a bog-standard MK2 Cortina. Or, say, the Alfa 75, widely regarded as a great car and the 'last true Alfa', but cursed with awkward looks, ergonomics, and the '80s Italian car' rep, which makes it worth a fraction of what it should be worth.
And let's face it, the pre-facelift 166's 'face' is definitely an acquired taste, and the Sportronic has a certain, erm, reputation, so it's unlikely to ever be worth much more than the sum of it's parts.
OTOH it should all be down to which one(s) the OP enjoys driving the most, not which one will be the most valuable.