That's the metaphor my mind goes to when I ask the question stand-alones or series. I absolutely love both, but I decided to compile a list of my pros and cons, but obviously these won't apply to all books and some are genre specific. At lot of this is personal opinion, so you may find you disagree with my points.
-Less material, so generally edited better
-Only one idea but more developed
-Less/no character deaths
-You don't have to wait for part two of the story
-You can only love or hate it, you can't get influenced by a horrible sequel
-It's over too soon
-Not as many main characters
-Things that happen must be constrained to the time frame
-The characters have more opportunity to be developed
-More things occur in the longer storyline
-Many plot twists
-New characters are introduced in later books
-Opportunity for extensive world-building
-You only have to learn about the world and characters once which sets you up for multiple reads
-Takes longer to read
-Story can get repetitive
-Main characters can become unlikeable
-The transition between books can be done badly
-Each book takes ages to release so you have to wait a long time for the next bit of the story
-The series can start off good but slowly get worse
I read series more often, but recently I've found some really good standalones. Goodreads seems to give me series suggestions the most which is the other reason I read series a lot. I love both book types, but if asked to choose Id go with series because that's how I grew up.
What about you? Which do you prefer reading and why?