It was recently announced that the Raspberry Pi (RPi) has sold 1.75 million units in the 1.5 years they have been available. That is seen by most folks as a screaming success. In contrast, the One Laptop Per Child project (OLPC) has sold about twice as many OLPC units in about 6+ years... yet it is seen by some as a quasi-failure.
Target Audiences - Both projects have targeted the education market. OLPC is aimed at general education and early grades whereas the RPi is targeted at the same and older age groups specifically in computer science education.
The OLPC has been sold specifically to governments and school systems and while they dipped their toes in the consumer market with the Give 1 Get 1 programs, those efforts were not well executed and as a result only became a small fraction of their sales. The bulk of the RPi sales have been directly to the retail market. RPi is still working on educational materials and it is still unclear how well it will do within school systems. Retail sales may still help with the RPi goals but to what degree is unclear. It appears the bulk of their sales are going to hobby type projects and I'm not sure if those qualify.
Copy Cats - The hardware of both projects launched new mass-market product categories because oddly the retail and wholesale mega-corps got scared and had to introduce competing products. The netbook did quite well for a couple of years but the pricing on more traditional laptops dropped low enough to practically eliminate it. There are a large number of ARM-based RPi like single-board computers (not counting the embedded market that pre-existed) but I'm not sure that any of those will be notably successful. RPi clones are somewhat overlapped by the mini-Android clone market.
Hardware and Pricing - Both projects have had unanticipated delays in their design and production phases but they made it through. OLPC ended up being more than double their target price, which appears to have been unrealistic... while the RPi, perhaps having a closer relationship to a component manufacturer, hit their targets. The OLPC is a more complete gadget whereas the RPi requires a significant amount of hardware extras before it is usable. While it is easy to overlook the extra costs associated with the RPi, they are definitely real.
Both projects have revisited their designs coming out with newer hardware releases. The OLPC is in their fourth iteration and they completely changed CPU arches yet the outsides look exactly the same. The second RPi release doubled the RAM without a price increase... awesome.
Software - One major difference is in software. The OLPC Project designed a custom user interface and several stock educational activities on top of Linux whereas Raspberry Pi hasn't had to do as much in the way of software. Both projects have successfully relied on the communities that sprung up around them to augment the software both provide but the RPi seems to have a ways yet to go with the software for their target audience.
Roots and Expectations - Given the similarities and differences between both projects, why is one more often perceived as a greater success than the other? I think a lot has to do with the roots and expectations. One had a big name and lots of media up front and was expected to "change the world" and the other, not so much. I think that is the main reason for the perceptions but there is certainly more to both projects than such a simplified type of judgement conveys.
Unanswered questions - Here are some of the questions that come to my mind. Did I leave any out?
How well will RPi do inside of school systems?
Will RPi rev their hardware like OLPC has with major changes? If so, how will it impact manufacturing costs and pricing?
Will any of the wanna-be products be able to significantly poach users away from RPi or will RPi do that themselves with a later model?
Does the current RPi model B have such a strong mindshare that a future model may be overshadowed by it?
What future plans does the OLPC project have?
How many more OLPCs could have been sold if they had added the consumer retail market as a target and executed as well in that space as RPi has?
OLPC has taken a small foray into the consumer market by allowing their name and look be to be used by one budget Android tablet maker. How well will that do and will there be others?
How exactly do these OLPC licensed third-party projects benefit the OLPC project?
And lastly, will any of those questions ever be answered??! :)
Conclusion - In any event, I'm glad we have both projects and wish them continuing success and a long future. Keep up the great work everyone. Will there be any other projects that make it this level? I certainly hope so. We definitely need more open hardware in the market.