Kevin,
A lot of folks like the collect "local" aspect of the set. Perhaps there is a team within the eight series that is where you are from, or born, etc. I live in Tennessee, so naturally I leaned that way with Nashville, Chattanooga, & Memphis, but I was born in Ky and have roots there so the Blue Grass League interest me a lot in from Series 6... There are so many different ways to collect this set. If you like printing freaks, then Series 3 has the OB-20. Hard to find in Orange border, but even harder to find in Red border imho. Collect them by pose, catcher gear, portrait, in action, and so on. I started with collecting 1 from every team in every series. A lot of fun and I could pick out the poses that suited my interest.
As for toughness, I generally agree with aforementioned posts on scarcity. What I have found though from collecting these the better part of 2 decades is Series 3, 4, 5, 6, 7, & 8 have players that are tough to find. It seems that there are pockets of rarity that you can only find by collecting them over time. There is no consistency.... Especially series 4, 7 and 8. Its a fun set to collect and you can collect very casually. Don't get in a rush and enjoy the True Monster.
