Novels for sure.
Novels have a lot more dinosaur involvement in them and you get to see more of the park.
If they ever do a remake that is exactly like the novels i think people would go bonkers with how much better it would be.
As others said the rex in san diego kind of ruined the lost world movie.
Good things from the novels that didnt make it into the movies-
JP: baby raptor playing in nursery, compys on the mainland, juvi rex killing ppl, dinos that climb trees, baby triceratops, stegasaurus being the sick dino, more characters and more inclusion of certain characters like gerry harding and muldoon, rex hunting hadrasaurs, hammond's home, rex swimming and chasing alan and kids on a raft, aviary and pteranadons (i think), muldoon rocket launcher tranqing the rex, see more of the infastructure of the park like the maintenance sheds and underground tunnels, hammond dying from compys...
LW: inclusion of more characters and better new ones, dodgson is back, a lot of time is spent seeing how the dinosaurs behave in their natural enviornment, better kids, the dart guns are actually used, and no rex in san diego scene.
Only downside to the first novel is the ending that seemed rushed to me and it saying costa rica bombed the island afterward to kill the dinosaurs which seemed way too extreme and didnt make much sense.