While we all have our own interests, and as such different projects strike each of us as worthwhile, I will give my thoughts on a few Boinc Projects, and their suitability for a given system. As I cut down and refined the projects I am running, I have only run a hand full of them across most of my machines. As such the projects I will focus on in this post are: Prime Grid, World Community Grid, eOn, Yoyo@ home, Climate Prediction and Einstein@ home.
Prime Grid - Avoid at almost all cost, not only does this tend to cause your machine to run extra hot ( hotter than usual for boinc tasks it seems), but especially lately, on no matter the machine, it tends to give bloated project sizes, with somewhat short deadlines for completion. While they do not enforce the deadlines strictly, it often causes the projects to be given High Priority status.
World Community Grid - Great choice especially if you like to support humanitarian projects. Often gives decent length time lines, and they do a good job of matching jobs to systems, with older systems usually being given less intense projects to crunch, often with shorter completion times allowing even these older system to crank out projects at a decent rate.
eOn - Not the most intriguing of projects from descriptions, but I have found on these older systems, it is my go to project. Less so now that its summer, and I brought the computer home from my office to have it crunch 24-7. I like this one for a machine that is sporadically turned on ( being on a campus with different schedules each day, and somewhat often not needing to turn on the computer for great lengths of time during the day) as especially on these older systems they seem to give out 10 minute projects. While they do not generate a lot of credits, its not a huge loss if you turn off the machine and don't turn it on for a few days and the deadline passes.
Yoyo@ home - This one seems to be developing a lot of the same problems as Prime Grid.
Einstein@ home - Behaves similar to World Community Grid, but a great choice if you are fascinated with Outer Space, and the Solar System.
Climate Prediction - I almost can't believe I am recommending this project for this, because it gives incredibly huge projects. But what took me a while to realize, is the deadlines for these projects are usually a year away, and even a sparsely used system should be able to crunch 500 hours in a year. Also I need to double check this, but it seems to periodically report in and grant credits, so if you like watching the credit numbers rise, its not like you are putting off bringing in credits for a month or so.