Both work the same, but have different operating logic voltages. You can't stack a big shield on it but for many small & simple projects the Trinket will be your go-to platform. In fact we even made some simple modifications to the Arduino IDE so that it works like a mini-Arduino board. We designed a USB bootloader so you can plug it into any computer and reprogram it over a USB port just like an Arduino.

The Attiny85 is a fun processor because despite being so small, it has 8K of flash, and 5 I/O pins, including analog inputs and PWM 'analog' outputs. It's our lowest-cost arduino-IDE programmable board! Perfect for when you don't want to give up your expensive dev-board and you aren't willing to take apart the project you worked so hard to design. We wanted to design a microcontroller board that was small enough to fit into any project, and low cost enough to use without hesitation. T rinket may be small, but do not be fooled by its size! It's a tiny microcontroller board, built around the Atmel ATtiny85, a little chip with a lot of power. It has built-in USB, more capabilities, and is comparable in price!

So while we still carry the Trinket so that people can maintain some older projects, we no longer recommend it. Deprecation Warning: The Trinket bit-bang USB technique it uses doesn't work as well as it did in 2014, many modern computers won't work well.

Adafruit trinket 5v power draw