In the photo above I am modeling the dress with a thicker black belt done up at the smallest part of my waist, again its because it helps add curves.
I really LOVE the look of the thick belt because it makes the dress look like more of a statement dress. I think that with a thicker belt it makes the dress look more casual. The big buckle adds texture and dimention to the dress. I would also wear this with a thick brown belt or any other coloured belt that would complement the fresh colour of the dress.
Because the belt is so big I would wear the belt over the cardie aswell as the dress if I decided to team the dress with a cardie for colder weather.
Over all I prefer the dress with a thicker belt so I have to say THICK has won this one :)
This dress is a really simple cut so if you're really clever you could even have a go of making your own simple teardrop necked dress (let me know in the comments if you are going to try and make a similar dress).