Hot Rod was the youthful...well...Hot Rod who, upon the death of Optimus Prime (which he caused,) was chosen by the Matrix of Power to lead the Autobots...
...and was transformed (redundant, I know) into Rodimus Prime!
He started out as a groovy futuristic Hot Rod:
And when changed into Rodimus Prime, he became a souped-up...Motorhome?!?!
Okay I know he's supposed to go from teenager to an old guy overnight, but at least he could have turned into a forties Ford or something classic like that. Not ALL old guys drive Winnebagos!
At least he was heavily armed, because "Those Decepticons are just damned hooligans, and if they smash my mailbox or put a flaming bag of poo on my doorstep ONE MORE TIME..."
They don't sell 'em like this at The Scooter Store!
I always thought it odd that both figures/toys were released at the exact same time. There was no "Oh wow, Hot Rod, a character I have grown to know and love, has evolved and changed into a seasoned warrior and leader." It was more like "Hey kids, look at this guy, cool huh? Now look, he's another guy. Didja blink? Sorry, you missed it. Buy these toys now."
"Thank the Matrix, I look twenty years younger!"
In 2004, in the Energon series of figures, Transformers released Rodimus...just plain Rodimus...the best thing to happen to Hot Rod since the day before he turned into Rodimus Prime.
First off, he's a Semi...and if someone is going to turn into (or is already) the leader of the Autobots they oughta' be a Semi. It's the way things are done, son. But Rodimus here isn't any old Semi. He's a rocket Semi...you know, the ones you see at the drag strips, shooting flames and haulin' ass. Yeah, that's my kind of leader right there, not a stinkin' Winnebago.
His head sculpt is even closer to the G1 cartoon look than the original figures.
He's impressive in bot mode as well. Nice flame highlights, and the wheels for shoulders really bulks him up. All the while his inspirations are undeniably there. A great homage to the Hot Rod/Rodimus figures of old. I don't know what his toyline/cartoon story are, so I just think of him as what Hot Rod should have become.
Rodimus is the shortest of the bunch. Part of the Energon series was a gimmick where two Autobots could be merged together to form a larger robot, and you could use any one with any other one. So they did a great job incorporating that feature while still maintaining a great robot and vehicle mode.
Hot Rod is great all around. A nifty vehicle, a solid robot, great sleek looks, and no extra parts to lose. He's always been a favorite.
Rodimus Prime is pretty cool too. His robot mode is very static, but his design is clearly a "grown-up" version of Hot Rod, and I did think that was cool as a kid. He's a single unit when in vehicle mode, which is a plus, and his vehicle mode is cool even if it is a motorhome. If you gotta pull over and nap, pull over and nap in style!