I like the fact that we've got all 3.
I love the final shots of people's tanks, they always looks so stunning, but once you've seen that sometimes it's nice to see how they got to that stage. Either 1 or 2 can provide that.
1 offers hope to people like myself who are still just starting out and are pulling the resources and skills together slowly but surely. It shows how others have done the same and offers ideas about various problems.
2 can show how to re-create an effect but you lose some of the transition and background info. Often 2 is a part of 1, cropping up here and there in between the warts and all account.
I update my journal in an irregular manner, spurts and bursts depending on what's been going on in my life and how much time I have to dedicate to the tank/internet! (which reminds me I really need to take some more photos and do a mini update... not least because I have some ideas for change and the last photos look nothing like the tank currently sitting in my room!)
Following a journal like Mark's is very different, you feel much more involved with what's going on (even though I tend to lurk more than post!) and every step is associated with its own discussion and debate. Everyone has something worthwhile to add and watching how the 'scape forms is fascinating
So I go with everyone posting what they have the time and inclination to post. If you like to see dramatic final effects then look at the final photos section and if you want to find out about the 'making of' then head on over to the journals and see if you can find it there.
At the end of the day if you prefer journals to be more 2 style than 1 then you can always skim a 1 type journal.
*edit* though having just read the question,
Which has more impact? It's depends on your definition of impact. If you mean 'hard hitting' then it'll be 3, people will always be more likely to go wow at a stunning photo. If however you mean impact in the same sense as researchers define impact - spawns the most papers, gets read by the most people, gets you the most acknowledgement, then I'd say 1, something that's updated frequently and sticks in people's minds is always going to produce most references and copy cats.