here are the specs for each one
12"powerbook
12.1-inch TFT Display
1024x768 resolution
867MHz PowerPC G4
256MB DDR266 SDRAM
40GB Ultra ATA/100
Combo Drive
NVIDIA GeForce4 420 Go
32MB DDR video memory
10/100BASE-T Ethernet
FireWire 400
AirPort Extreme Ready
Bluetooth built-in
VGA & S-Video out
just 10.9 inches wide, 8.6 inches deep, 1.18 inches and weighing a mere 4.6 pounds
17"powerbook
17-inch TFT Display
1440x900 resolution
1GHz PowerPC G4
1MB L3 cache
512MB DDR333 SDRAM
60GB Ultra ATA/100
SuperDrive
NVIDIA GeForce4 440 Go
64MB DDR video memory
Gigabit Ethernet
FireWire 400
FireWire 800
AirPort Extreme built-in
Bluetooth built-in
DVI & S-Video out
just 15.4 inches wide, 10.2 inches deep, 1.0 inches and weighing a mere 6.4 pounds