If you do that comparison on the LG site....there isn't a lot of difference between them at all!
The only differences I can see (apart from dimensions) is the lowest model 620T has the 'basic' upscaler, not the 'plus' and it probably doesn't have local dimming - it's not totally clear tbh as that section is just blank and doesnt say NO.
Also the 620T comes with 4 pairs of 3d glasses, the others have a 5th clip on pair.