The Alpha is modernized to have a nicer bolt throw that does not make it hard to mount a scope with low rings and has a nice flush double stack magazine. Likely easier to find spare mags down the road as well if needed.
If you really like to shoot wood stocks and iron sights, don't want or need a scope, then you can look for and pay more for a used 527.
The set trigger is neat, but the trigger on the Alpha is nice and easily adjustable for weight.
Years ago I was buying a rifle from a guy and he also offered me a 527 for around $600 but I declined, latter I regreted that decision, even more when the asking prices for used 527's went way over $1000. This was before the 600's came out. I think today if both guns were new in the box infront of me, same price, I would still take the newer model.