I'm not a van of same colour varidiyan. I've worked with both Same colour and Jori's (coloured pairs). Here are the 2 differences I see.
1) Obviously the stage is more colourful
2) Complexity of formations & Transitions - This is something that I have found to be more difficult yet more enjoyable while making a set for Jori's. It is much easier to work with formations while having the entire team wearing the same colours, where as, with jori's the transition must work out along with where the jori's are places on stage. You can have the jori's who stay side by side, or who are on opposite ends of the stage. It's a little hard to explain. It may make more sense with pictures, but that would take too long... so I hope that made sense. lol
As for the small vests, one of our team members went to India recently and orders some new suits. He found out that the reasoning behind the small vest is because the material would fold where the vest meets. Nachdi Jawani also had small vests at Idols and the India team that competed at Bhangra Nation this past year did aswell. I dont think its a GS thing. lol