I own highly sought-after models from both brands. For those wondering which is better, I'd summarize: there are no winners or losers, at least not for me. A fair comparison based on price differences would be more accurate.
Both watches prove their good quality status. However, I don't know how clearly the indices are visible in the photos, but Longines' polished indices are more legible and showcase a higher level of craftsmanship. Seiko opted for a more matte and brushed finish, but that wasn't the right approach. The HC has two anti-glare coatings, while the 62 has one.
The bezel is thicker and ceramic on the HC, making it more visually appealing. And most importantly, the ceramic-steel section on the HC has a smooth transition. Unfortunately, Seiko disappointed somewhat with this model. The bezel sound is much better on the HC.
Seiko excels in scratch resistance. Their watches are virtually scratch-resistant. Additionally, Seiko's case design is rounded, as if under some kind of protective coating. I also really like the darker tone of the steel case on the 62 model. Unfortunately, the HC model doesn't quite reach that level. The brushed case parts stand out more.
Both watches have the same power reserve, but the HC operates at 3.5 Hz, which is noticeably smoother than the 3 Hz model.
The HC changes the day suddenly at 23:59, while the 62Mas changes gradually from 23:15 onwards.
I consider both watches to be very heavy-handed. Sometimes I can't even decide which one to get. You won't regret whichever one you choose.