Get both, and see which works best for your little one. If you do the toilet seat, make sure you get a sturdy step stool. I used both but started with the potty seat, I kept it in what ever room we were in and kept my son diaperless, and told him to keep sitting on the potty if he had to pee. We made a game out of sitting on the potty.. He went the first day on the potty once or twice, and he had a few accidents, but he was super proud when he went. I acted all crazy hopping around, and did a stupid little dance for him.. He giggled and wanted to go even more to see mommy act like a maniac.. Then we tryed the toilet, he was a bit nervous, and sat down but wasnt ready for that for a while, he would just sit there, and look at me, like what now. But he moved forward quickly and was trained within the month, even at bed time.. Hope this helps!
M.