Both Bocconi and HSG has good exchange network and double master degree program.
but given you had already some year of working experience, and had born oversea, I guess you will find an internship in the industry will be way more useful than a exchange or double degree.
getting 2 degree in the same discipline in 2 similar level school don't have a significant marginal benefit.........but an exchange may be useful in moving one to another place.
I don't consider Bocconi or HSG being a good choice for those who plan to go HK at the end. It is just the difference better, not good vs not very good...
Given OP had 3.5 year of working experience, but a poor GPA, one good alternatives is to do a MBA in HKUST, CUHK or HKU.
FYI, for Asian networking, HSG is working more on SG instead of HK. As far as I know, exchange program is the only thing they have on this side.
(given the majority of the students in these school are European, and don't speak Chinese, it is way more reasonable to develop the network in SG than in HK, though it may not be something OP wants.)
Both Bocconi and HSG are target school for London BB, and there should be career event from various firm and on-campus interview for both of them.
Towards London. Bocconi is slightly better not because Bocconi is a better school, but simply because their finance student are way more motivated to move out of the region as they are in Italy, while HSG has Zurich + Frankfurt as the local job market.