Are there other options where you could both find reasonable opportunities in a third city? Why not look at all options and see what you can find?
My DH and I went through this -- we dated long-distance (east coast to desert southwest in the US); then we got engaged; then we said, damn, we should figure out how to be in the same state. Both of our jobs are fairly specialized, so he looked in my area, I looked in his, and we also looked in other cities where we thought there were good options for both of us. In the 20+ years we've been married, we've ended up living in his state, my state, and a third state entirely, because our baseline criterion was that we both had to have jobs that we enjoyed, so when one situation didn't work, we found another.
YMMV -- not saying that you need to make that same decision; if one of you cares less about the job than the other, it is equally reasonable to move where the one who cares more has the best opportunities; or if one situation provides a better option to FIRE quickly, and that is the ultimate goal for both of you, then go there. Etc. Point is just that the options are not binary, and the same answer is not right for everyone.
I would not, however, consider this unless I was confident the relationship was permanent. Again, YMMV; I just wasn't going to give up my awesome job and family and friends for a maybe.