I try to run a mix of about half-published / half-homebrew adventures, often running the homemade ones in between the published ones. Here's some of the reasons for doing one or the other:
Published Pros
- Usually requires less work to prepare adventure.
- Often these have good stories and innovative encounters that I may not have thought of on my own.
- Even if I don't run an adventure I purchase, I can usually harvest NPCs, encounters or other ideas from it.
Published Cons
- Not always able to fit into my campaign. Many adventures make geographic assumptions that may not easily fit. Others make historical, political or religious assumptions that may be too hard to reconcile.
- A common problem is that the reward level is out of whack requiring heavy modification to gold or items listed as treasure.
- Many encounters, puzzles or traps make assumptions of party make-up. For example, a recent adventure I ran out of Dungeon magazine required use of an arcane scroll that only wizards and sorcerers can use. Party had none, and the bard and rogue didn't have enough points in use magic device to use it. I worked around it by planting a potion that allowed a major boost to use magic device, but felt this was kind of a cheesy solution.
- Reading and familiarizing myself with a big adventure can take several hours. If modifications are needed, it can become almost as much work as writing my own adventure.
- Players do unexpected things which sometimes the published adventures don't expect. This can affect home-made adventures as well, but in those cases, I usually have a pretty good feel for how the party will react.
Home-brew Pros
- Can tailor encounters, traps and story to party which can lead to a story that the players are very interested in.
- Can bridge adventures much easier. Explain transitions between other encounters in a more believable manner, etc.
- Related to previous point - I find that I often come up with with encounter situations that are much more balanced or challenging to my party. Might involve maps, creature mix or other aspects.
- Feeling of ownership for creating it yourself. Sometimes I get congrats from my players like, "That was a great encounter," or "How'd you manage come up with that? It was really creative!" Makes me feel good to hear that.
Home-brew Cons
- Takes a lot of time. I find that prepping for a typical 4 hour session takes me about 8 hours of work on average. Less for something simple or repetative, but even more for something with a lot more variety and backstory.
- Sometimes you overlook the obvious. I've had adventures go astray when I totally overlooked something obvious like forgetting about certain character abilities. This doesn't happen very often, but when it does, it can be frustrating.
- Can get burned out trying to think up a cool adventure. This is another reason to alternate between published and homemade stuff.