There are differences between the definitions of the two. Microcontroller is actually a microprocessor with a bunch of built-in, built-around peripherals. Such as ADC (analog digital converter), DAC (digital analog converter), EEPROM or other memory, comparators, general timers, RTC (real time clock), UART, I2C, SPI etc.
So while there are many overlapping ...
Engineering is the art of compromise. You usually have to juggle with several parameters, some of which may be at least partially contradictory.
For instance, you could have to find the best compromise between:
UI and ease of use
ease of development
A microcontroller will ...
You can trigger Record and Play from pins described in  and printed in board. Audio signal can be saved to .wav with ALSA library  and saved to SD card. Then it can be sent as HTTP POST to server.
One issue is that ISD1820 is meant for looping, so you have to manually stop recording when time is 20sec.
Are you really only asking which will draws more current? In either case, the cost will be negligible.
I would have made this a comment, but it grew too long.
What, exactly, are your requirements for a webcam? It is just for Skype & the like, or for security?
Must it ...
Lots of single-board computers support android in their BSP. It's often less porting effort than Ubuntu since the SoCs generally have mobile as a primary market. If you need it, this can give you more processing power than the more common Raspberry Pi 3. For example, the LeMaker HiKey
which is an 8 core A53 with up to 2GB of RAM. Other options worth looking ...
You could potentially install Android 7 on a Raspberry Pi 3 if you wanted to run that, as described by the MagPi magazine.
The binaries can be downloaded here, although I can't tell if the performance will be that great, or if it will be sufficient to run an AR application. You might just be able to use a USB camera (according to this discussion) although ...