Sussex or Leeds

I want to study international relations in uk, and I come from Hong Kong.

I found that the Sussex reached a higher ranking in this field, however, other aspects are lower than Leeds, such as employer reputation.

If I more emphasis on work experience and job, which one should I choose ?
And, if I more emphasis on quality of education, which one should I choose?

Disagree, I'd argue that Sussex has a superior IR department, and this is reflected by its reputation among academics in the field. I'd be cautious about trusting league tables (I'm sure you could find one that puts Sussex above Leeds, for example).
Also, given the politics surrounding the TEF, I would be sceptical of that too - I believe Sussex boycotted the National Student Survey, which feeds into the aggregate Teaching Excellence Framework score, possibly negatively affecting it whilst not necessarily being a good indication of teaching quality.

Furthermore, these stats about '96% employed' or whatever are pretty much useless unless they're gradated by level of employment. I'm sure I contributed positively to the University of Bristol's vital statistics whilst working in a call centre and for Deliveroo.

I appreciate that as an overseas student, you don't have much to work with besides rankings and scores and league tables, but they are not generally that trustworthy.

You need to look instead at the course content - what do you want to learn about? What is the department's research profile? Are there any particular academics who you want to learn from? Ask them to send you indicative reading lists so you can find out what kind of literature you'll be working with. In short - if you want an accurate picture, you'll need to do a bit of digging, and not relying on pre-packaged, massaged, political statistics.

As the above poster pointed out, these are both good choices and you'll do well with a degree from either of them - the difference in 'value' of their respective degrees in the job market is probably negligible. However, all other things being equal, I'd suggest that Sussex is a better place to study IR - although you'd need to look into this further to decide if this is true for you.

Good luck!