Hello,
The Seeduino seems stronger and yet it costs less - what's the deal with that? I'm trying to make a 64x32 led screen with ability to stream video to it via computer serial port (usb). Does the seeduino mega have any advantage over Arduino mega? Help me decide which one to buy 
Or maybe there's something even stronger?
I think the serial port is going to be a serious bottleneck.
64 x 32 = 2048
If you want a seemless stream, you need > 25 fps.
Baud = 2048 * BIT_RESOLUTION * FPS
For now, lets assume a 1 bit resolution (that is, led on/led off) [monochrome]
Baud = 2048 * 1 * 25 = 51200
Then you need a minimum baud rate of 51200
In addition to simply recieving the data, you need to output the data to the screen.
How do you plan on implementing this?
Sounds like a cool and challenging project.
The mega has 3 serial "ports" 
I think that is not a problem.
The mega has 3 serial "ports"
I think that is not a problem.
Thought it had 4 - 1 default and 3 additional. I was thinking of using arduino just as stream through - dividing the screen in 4 (or 8) separate led matrices which would be controlled individually by separate microcontrollers and led drivers from the base one which would be connected to PC.
I've seen it being done with peggy2 with greyscale support with no flickering.
LINK: http://planetclegg.com/projects/Twi2Peggy.html
Umm... So any pointers on which board (Speeduino or Arduino) is a better choice? And where to buy it - straight from seedstudio or nkcelectronics? If it's arduino, elioness?
The mega has 3 serial "ports"
No, the Mega has four hardware serial ports, the standard serial port and three extra.
As far as application power goes there is no fundemental differences between the Arduino and Seeeduino Mega boards. The Seeeduino just has a few extra features like manual switchable automatice reset, manual switchable power source. It also has 16 extra I/O pins brought out to solder pads, they aren't supported by the Arduino IDE core but you can use them via direct port access. Also the Seeeduino board is smaller (same form factor as the standard Arduino board) and uses smaller USB and external power connectors. Also the board's reset switch is accessable even with a shield installed.
I bought the Seeeduino version so I am not impartial but both Megs are great offerings.
Lefty
Oh...I new i had it wrong... :-[
But since the Seeduino has more I/O pins i'd say you get that one...
Or get a Mega clone !!!!
I can get a Arduino MEGA for £57 and a Seeeduino Mega for £37, But finish up with a Mega clone off ebay for £25 inc p&p / taxes and very happy with it for less than half the price.