Switching from Yasmin to Yaz, is there weight gain or weight loss?

I've been on Yasmin for 6 years (I'm 21 now) for PCOS. I came off it about 5 months ago as I was still having a lot of break-through bleeding. I noticed I put on weight and felt bloated while on Yasmin and since coming off it I have lost it all. My doctor wants me to try Yaz and I wondered if anyone had made this transition or knew the side effects of Yaz? I really don't want to gain weight going on it!!! I'm 5'2" and weigh just under 9 stone currently. So like most women I'd rather it had a weight loss side effect if anything!!!