Starting with accelerometers, which to choose?

So I am trying to buy a low cost accelerometer to use with my Arduino and PIC projects. I don't know much about them, and would appreciate some advice.

I have come across two which interest me: the ADXL345, and the MMA7361. Those seem to be the cheapest around with a good record. If there are any others, please let me know what you recommend - or help me choose between these two.

With that said, I was looking at the ADXL345 on eBay, and found something weird. http://www.ebay.ca/itm/Arduino-Triple-Axis-Accelerometer-Breakout-ADXL345-/130492972527?pt=LH_DefaultDomain_0&hash=item1e61fcbdef

http://www.ebay.ca/itm/ADXL345-3-axis-Digital-Sensor-Acceleration-Module-Arduino-/270904019741?pt=LH_DefaultDomain_0&hash=item3f13234b1d

The one in the first link is cheaper, but also smaller. It seem like the same thing as the second, but I am wondering why it is smaller and looks like it has less components. I do know it is missing the pins, which I can solder on myself if I purchase it. But anyways, why do they physically seem so different?

Thanks in advance everyone! Love this stuff :)

The ADXL345 chip itself is designed to be used with a 3.3V power supply and signals. The "board with more components" is designed to be usable with either a 3.3V or 5V supply and signals ... granted their implementation does not use true level conversion on the signal lines.

The MMA7361 is an analog device; its X/Y/Z values are read as a voltage from 0 to 3.3V and can be read with the Arduino's 10 bit precision. The ADXL345 has a digital (I2C or SPI) interface and can be read with 13 bit precision. As with any analog vs. digital discussion, the analog is easier but the digital is faster and ...digital.

Make sure the chip you get has the sensitivity and range you need - some go up to +/-2g, some to +/-8g, some much more. 2g will give you orientation but won't handle gestures without overloading, 8g is a better range for that.

For an analog device sometimes the breakouts have LPF components on. This might not be what you want if you want to detect tap gestures.

Thank you so much for the information, I really appreciate it!

Everything makes so much more sense now.

So I pulled the trigger on the MMA7361 for now. I figured it would be easier to use initially. Perhaps I will purchase the ADXL345 soon after I use the MMA, understand its limitations, and further decide on what my specific requirements are.

Thanks again!