Earlier bolts (Russian) have spring loaded firing pins (as mentioned in an earlier post). Whether this is an real plus, or not, depends on whether you believe "slam fires" are a real problem or a marketing opportunity for after-market sellers. I put the after-market bolts in the same category as head space gauges for Mosins - marketing opportunity; a solution looking for a problem.
The real plus of early bolts is the extractor can be easily removed for cleaning (or losing). This "problem" was solved by pinning the extractor in later models so you can't clean it as well but you can't loose it as easily either. Older (1951 and prior) don't have chrome lined barrels which is a problem if you don't clean your rifle the same day if you fire corrosive ammunition.