Personally, I think that if you want to use those two masters as a stepping stone for the US ph.d, then you would be better to go for UC3M as it offers you a scholarship. I do no think that the marginal benefit of attending UBC master is worth more than a 2-year-long fund. (However, if UBC offers you a TA, then it is a way to clear choice.)
If you think to work in Asia, specially in HK, the brand of UBC could add you some advantages to get a better job.