Dr brown bottles

Starr • Baby #3 Coming Soon! Selenya Avery born July 2016! 🎀 Angel Baby Lily🌸👼🏼 Secilia Elizabeth born October 2021 🌈💖 Maverick due May 2025 💙
What's the difference between the wide neck and skinny neck bottles? The skinny connect to my pump but I have a pack from my baby shower debating Whether to just exchange them for more skinny. 
And why do they tend to leak? Is there a way to prevent this?