Year Model Engine Transmission
2003-2008 Base 1.8l 1ZZ-FE 4-speed auto and 5-speed manual
2003-2008 AWD 1.8l 1ZZ-FE 4-speed auto
2003-2006 GT 1.8l 2ZZ-GE 6-speed manual
2009-2010 Base 1.8l 2ZR-FE 4-speed auto or 5-speed manual
2009-2010 Base 2.4l 2AZ-FE 5-speed auto or 5-speed manual
2009-2010 GT 2.4l 2AZ-FE 5-speed auto or 5-speed manual
2009-2010 AWD 2.4l 2AZ-FE 4-speed auto
2003-2004 models have a cable-throttle, 2005-2008 have Drive By Wire (DBW). 2005/2006 Vibe AWD still had cable throttle.
2003-2006 Vibe GT with the 2ZZ-GE engine require 91 octane, or above. Any less may cause engine damage over time, and reduced performance.
Body
The 03-08 Vibes could come equipped with an OEM body kit, which included front fascia extensions, side skirts, rear bumper extension, midgate spoiler, and upper spoiler.
While the 05+ Vibes were revised, the same body kit can be fitted to all first-gen Vibes.
There are a number of body differences within the first gen Vibes


Some first-gen Vibes have tucked-in side skirts (such as the ones that came stock on my Vibe), mostly monotone Vibes. The flared skirts (pictured above) were a TSB offered since the unpainted and tucked skirts would get marred up pretty significantly (allegedly). Thus, after a certain year they're standard, but some before that year do not have them (TSBs aren't a required thing like recalls).
Mirrors: 03/04 had unpainted black mirrors, while 05+ monotones had body-colored mirrors.
Body/lip kit:

1. Upper deck spoiler
2. Midgate spoiler
3. Rear bumper fascia
4. Extended side skirts
5. Front fascia extensions
Weights:
03-08 base manual: 2701 lbs
03-08 base auto: 2778 lbs
03-06 AWD: 2976 lbs
03-06 GT: 2800
09-10 Vibes had minor differences as well. The AWD came with a factory roof rack, while the GT had a factory body kit with spoiler and big fog lamps
Base

AWD

GT

09/10 1.8L base manual: 2856 lbs
09/10 1.8L base auto: 2900 lbs
09/10 2.4L base manual: 2975 lbs
09/10 2.4L base auto :3055 lbs
09/10 GT manual: 3075 lbs
09/10 GT auto: 3155 lbs
09/10 AWD: 3155 / 1430
Engine
1ZZ-FE
1.8L
Bore = 79 mm
Stroke = 91.5 mm
Horse Power = 130 HP (120hp in Vibe AWD due to exhaust routing)
Compression Ratio: 9.5:1
SFI Fuel Injection
Unleaded

2ZZ-GE
1.8L
Bore = 82 mm
Stroke = 85 mm
Horse Power = 180 HP
Compression ratio: 11.5:1
MFI Fuel Injection
Premium Gas ONLY

NOTE (courtesy of shaeet):
03' Vibe GT's 2ZZ engines had NO smog pump & lift engagement was 6200RPM.
04' Vibe GT's have a smog pump & lift engages at 6400RPM.
05 Vibe GT's also have a smog pump and lift was raised to 6800RPM.
Swapping ECU's between an 04 and 03 is possible without any wiring but swapping a 03 ECU into a 05 require PIN's to be rewired. Corolla9.com has a lot of info on this since the Corolla XRS was sold in 05-06 and swapping matrix/vibe 03 ecu's is a common practice there. ALSO worth noting, the 03 ecu eliminates your smog pump if you have a 04-05, you can unbolt that extra weight & plug the hole coming from the exhaust manifold.
2ZR-FE
1.8L
DOHC 16-valve
Bore x Stroke = 80.5 x 88.3 mm
Compression Ratio : 10.0:1
134 HP
Unleaded

2AZ-Fe
2.4L
88.5 mm bore
96.0 mm stroke
Compression ratio: 9.6:1
158 HP
Unleaded

Interior
03-08 had the exact same interior, with the main/only difference being that the 03/04 models had a two-deck center console lid, while the 05-08 had a single-deck. Color for seat cloth was either a dark or light grey.


The cigarette lighter could have either been covered, or had a green ring around it. Those with the green ring had the Smokers' Package added, and came with an ashtray that would sit in the cupholder. From my experience, it was a popular option which dealers added, but wasn't necessarily ordered for a smoker. Also, the 03/04s have a 12v outlet in the center console. 05-08s don't, but the wire harness is still there (in case you want to add your own).
03/04 center console

05-08 Center Console

(Thanks to user GMJap for posting these pictures a LONG time ago)
09-10 Vibe had similar interior, with 2010 getting a silver shifter plate for the auto instead of black
09:

10:

Gauge Clusters
There was a color change from 03 to 04. 04 to 08 have the same gauge cluster color pattern
03 was all red (top) while 04-08 had white numbering with red outlines (bottom)

*note: upper cluster is GT model
03/04 gauge clusters are swappable. 03/04 clusters cannot be put into an 05-08 Vibe and vice-versa. 05+ clusters will beep at you if you don't have your seatbelt on.
09-10 cluster:

Wheel information
Lug pattern:
-03-08: 5x100
-09-10 1.8l: 5x100
-09-10 2.4l: 5x114.3
Bore:
All 1.8l: 57.1mm
All 2.4l: 54mm
Offset
All 1.8l: 34-42mm
All 2.4l: 39mm
Factory Wheels
All 1.8l Vibes, from 03-10, had these hubcaps:

09 1.8l had no alloy wheel options
03-08 16" alloy

03-08 17" alloy

Not a GT wheel - optional for all 2003-2008 Vibes
09-10 2.4l base/awd hubcaps

09-10 2.4l base alloy (17")

09-10 AWD alloy (17")

09-10 GT alloy (18")

All rims were wrapped in Goodyear Eagle RS-A all-season tires, except for the 03-08 17" rims. They had summer-only Dunlop tires. The 09/10 GT 18" rims were equipped with Goodyear Eagle F1 A/S-C all-season tires.
OEM Tire Sizes:
205/55/r16
215/45/r17
215/50/r17
215/45R18
EPA MPG
City/Combined/Highway
03/04 Vibe base manual
25/28/33
03/04 Vibe base auto
25/27/31
03/04 Vibe AWD
22/25/29
03/04 Vibe GT
22/24/28
05-08 Vibe Base Manual
26/29/33
05-08 Vibe base auto
25/27/31
05-06 Vibe AWD (AWD discont. in 06)
22/25/29
05-06 Vibe GT (GT discont. in 06)
22/25/29
09-10 1.8l manual
26/28/32
09-10 1.8l auto
26/28/31
09-10 2.4l manual (GT and base)
21/24/28
09-10 2.4l auto (GT and base)
21/24/29
09-10 AWD (2.4l 4-spd auto)
20/22/26
All for now, may add modifications to post later