First, what exactly do you want to have in your collection? Here are some facts:
Buster Optimus PrimeBuster Optimus Prime is a shiny repaint of the original toys. It does have two modifications: the gas tanks can be removed and transformed into a blaster, which puts it a step up from the original. Also, he features a head without a mouthplate. The Optimus in the 2-pack with Leader Jetfire, is a Buster, but with the regular head. He is expensive though, being a Japan-only release.
Jetwing Optimus PrimeThis is a more extensive retool, with a new abdomen to make it accurate to the updated model seen in Dark of the Moon, and removing the swing-out blades. The back has also been reworked for the jetpack to be attached. And yes, he retains Buster's gas tank gun.

He is pretty big and wide, hope you have the space for him. He's about to be re-released again in Asia with chrome pieces and G1 striping on the wings.
Striker OptimusA minor adapted version of Jetwing, with again retooled gas tanks. This one comes with a shield and a new blaster which can be stored in vehicle mode, or used to create an armed Stealth Force Mode, which looks amazing. This one is also about to be re-released in Asia, this time with the blades from previous movies added in as hand-held weapons.
Personally, I'd pick Striker.
The resident Rewind... well, half of one

- Jelze Bunnycat =:3
Looking for:
- TR Furos (Hardhead's head) and Crashbash (lost him

)
- PotP Punch head
- TR Galvatron right arm (the gun one)
- CW Brake-Neck/UW Wildrider, CW Offroad
- TR Twinferno & Grotusque
- Greenlight, Lancer and PotP Elita-1
- Legacy Core Slug, Sludge & Snarl