Both TGD and TIV are small airports which only takes a million passengers a year each, compared to say Newcastle with 5 million, and that is considered a small UK airport. Tivat gets busy in summer with all the Russians that like to holiday there, whereas TGD has a steady flow through the year. TIV suffers a bit from cross winds being close to the sea and a slightly awkward approach, but I'd imagine 99% of flights don't divert. TGD is a modern concrete and glass terminal, 12 years old, similar to many East European airports built recently. TIV is a bit of a mix of buildings, with T2 being new, T1 dating from the 1970s.
See previous discussion here:
BA Lounge Database | Europe