Differences between 70, 71, 72, 73 topps?

[JTysver]

1970 is not too hard to complete. The higher numbers can sometimes be hard to find because there are so many of them when you account for the semi-highs. There really is not killer rookies which drive the price up, although the Nolan Ryan card can be a little costly.

1971 is not too hard to collect if you don't want higher grade. Once again, no killer rookies.
If you want higher grade, its a bitch to complete.

1972 is hardest to complete of all the high number sets from the 1970s in my opinion. It is easy as anything to complete a low number set of these.

1973 has the Schmidt Rookie and it's also a high number. The high numbers, in my opinion seem to be somewhat plentiful.

If I were to have a choice of building any of these sets, I'd build them in this order...

1971 (because its so tough to build in high grade)
1972 (the high numbers are in higher demand than all of the others)
1973 (actually my favorite and first year I collected) and
1970