ST produces some of the most cheap development boards: the Discovery series. We have already reviewed the Discovery F0, comparing its features with Arduino and MBED https://www.hwmakers.eu/microcontrollers/stm32f0discovery-review/
ST Discovery F0 is cheaper than both MBED and Due but it is almost four times bigger than MBED and the last one is simpler to use, thanks to the excellent job made by the MBED team and by the community.
Digilent develops one of the most interesting developing board compatible with Arduino, chipKIT UNO32:
In our opinion this board is a lot better than Arduino, has been designed using better components, is well designed and has got a better layout, is more powerful and is cheaper. The board can be programmed using Microchip MPLAB or with a customized IDE very similar to the one used by Arduino:
The UNO32 is based on a 32 bit microchip microprocessor, model PIC32MX320F128 and can be used with many Arduino shields but remember that this board is not 5V tolerant. You can find more details on the official page: http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,892,893&Prod=CHIPKIT-UNO32
Now we want to spend some words about one of the most well designed circuit for the internet of things (IOT): Openpicus Flyport http://www.openpicus.com/site/products
Flyport is based on a microchip PIC24FJ256 and a WIFI module of the Microchip MRF24W series. The framework developed by the Openpicus team makes easy the programming of the PIC microcontroller and hides most of the programming complexity in order to have a very friendly way to develop IOT systems with a customized web server which is developed within the framework. It is very fast to get start with the Flyport using the Grove Nest board and its sensors breakout boards:
The MK802II is based on SOC Allwinner A10 but the latest version (MK802IV) has been designed around a 4 core chip. The 802II is distributed with Android Ice Cream Sandwitch 4.0.4 but is possible to use some optimized linux versions:
http://store.cloudsto.com/downloads/lubuntu-1204-rikomagicuk.7z (Lubuntu 12.04 LXDE).
Linux can be installed on a microSD so the original Android system is not delated and it is possible to go back to previous OS anytime.
There are many other development boards that can be compared with Raspberry Pi and their number is growing every day. Raspberry Pi has began the challenge and we makers are ready to choose the winner.
Conclusion: there is not a real winner because there is not in absolute the “best” development board but it depends on the application you have and its requirements. You can choose from a huge number of alternatives: you can looking for the most powerful (but it is not always the best solution), the one which requires less power, the cheapest, the smallest, the simpliest to be programmed or only the one you prefer.