Noodle's right. Eggs are the best. Here is a detailed breakdown of each holiday variant in order of best to worst and the reason why:
1. Eggs: The eggs have the ideal size, thickness, and shape to allow for the perfect ratio of chocolate to peanut butter. Their shape is simple enough that it doesn't get distorted or broken during shipping, which is a huge problem with some of the other variants. These are also the last holiday variant available until mid August, so you have a full 5 - 6 months to enjoy them. There were Reese's eggs in a grocery store near me well into June.
2. Pumpkins: These aren't quite as thick as the eggs, but they are slightly longer and wider so it balances out. You get a bit more chocolate taste than the eggs due to the different ratio of chocolate/peanut butter, but that isn't necessarily a bad thing. Their shape is mostly round, so like the eggs they rarely break during shipping. Really, the biggest problem with the pumpkins is their availability. They are only widely available for around 2 months, and almost immediately after Halloween they start to vanish because the Christmas stuff starts replacing them.
3. Trees: I look at Reese's Trees as deformed eggs. They're basically the same chocolate/peanut butter ratio, but they have that kind-sorta-vaguely-resembles-a-tree shape. A lot of times these come out so deformed that they are pretty much identical to eggs. That isn't necessarily a bad thing since the eggs are awesome, but I'd prefer they actually look like they're supposed to. These also tend to have a slightly smaller availability than eggs and pumpkins since Xmas isn't as big of a candy holiday as Easter and Halloween. They stick around till February-ish, but overall they aren't lining as many grocery store shelves as eggs and pumpkins do.
4. Hearts: These have a similar chocolate-to-peanut butter ratio as the pumpkins, but their shape is their biggest downfall. Very often the pointy part at the bottom of the heart gets mushed or completely breaks off during shipping. They also suffer from an availability problem like the pumpkins, only worse, because a) Easter stuff greatly overshadows and replaces Valentine's Day stuff; b) Valentine's Day candy is produced in MUCH smaller quantities than Easter, Halloween, and Xmas. You have maybe a month to enjoy these, if you're lucky.
