AVR

This page will not explain why you should use AVR chips or why PIC is better/worse. It is more the other way around - if you want to use an AVR chip - which one is a good choice. Capabilities, size, and cost are basically the main factors.

ATtinyX5

With 8 pins these are the smallest chips. Advertised with 6 digital I/O lines, but I strongly recommend not to use the reset line - which means 5 usable I/O lines. Older chips (like ATtiny11, ATtiny12, ATtiny13, ATtiny15, ATtiny26) should not be used. I do not use the ATtiny13A either, because the fusebits are different and the memory is pretty small (I rather spend the additional 20cents to get a ATtiny25.

ATtinyX5

Flash
RAM
EEPROM
1 chip
10 chips
25 chips
ATtiny13A
1k
64
64
$1.40
$1.20
$1.07
ATtiny25
2k
128
128
$1.66
$1.42
$1.15
ATtiny45
4k
256
256
$2.13
$1.73
$1.34
ATtiny85
8k
512
512
$2.84
$2.31
$1.78

ATtinyX4

With 14 pins these are very powerful chips, best for most projects. More IO pins than the ATtinyX5 and just a few less than the ATtiny2313.

ATtinyX4

Flash
RAM
EEPROM
1 chip
10 chips
25 chips
ATtiny24
2k
128
128
$1.91
$1.55
$1.20
ATtiny44
4k
256
256
$2.15
$1.87
$1.59
ATtiny84
8k
512
512
$2.90
$2.52
$2.15

ATtiny2313, ATtiny4313

ATtiny2313

ATtiny2313

Flash
RAM
EEPROM
1 chip
10 chips
25 chips
ATtiny2313
2k
128
128
$2.26
$1.84
$1.42
ATtiny4313
4k
256
256
$?.??
$?.??
$?.??

ATmegaX8

The Arduino line.

ATmegaX8

Flash
RAM
EEPROM
1 chip
10 chips
25 chips
ATmega48PA
4k
½k
¼k
$2.58
$2.22
$1.86
ATmega88PA
8k
1k
½k
$3.87
$3.15
$2.43
ATmega168PA
16k
1k
½k
$4.08
$3.77
$3.41
ATmega328P
32k
2k
1k
$4.30
$3.70
$3.30

ATmegaX4

ATmega644P

ATmega644P

Flash
RAM
EEPROM
1 chip
10 chips
25 chips
ATmega164P
16k
1k
½k
$4.82
$4.14
$3.56
ATmega324P
32k
2k
1k
$6.02
$5.18
$4.45
ATmega644P
64k
4k
2k
$7.76
$7.22
$5.70