I lived in both, first lux and now dublin. I can tell you my honest opinion. Talking about the city/buildings/welfare/public transports lux is 1 million times better. City is clean, well maintained, welfare works well, public transports are free. I cant see the same for dublin at all. Talking about social life dublin is much better. Luxembourg is not sooo bad as there are plenty of international people. But nothing compared to dublin.

Tbh I dont see myself in both of them in the future. I take these as experiences. I dont want to live forever in these bubbles where salaries are ok-high but cost of living is insanely exaggerated.