Wow, bold claim! I have never heard of another developer claiming to have done this before on any platform!

Forza surpassed Gran Turismo in realism? Really?
I think you would find quite a few (Read: the majority of racing fans/enthusiasts) would highly disagree with you there.

Community features have not been seen for either game, nor have the visuals.
I find a comparison of either a tad immature at this point.

^ To all.
Based on info given about GT5 by Polyphony, it barely matches Forza 2 for community features. Also based on GT5P experience online, its not just a bit behind but a long way off the racing experience that Forza 2 provided online. Admitadely the lack of any punishment for hitting a player up the arse made the game more like mario Kart.

All in all niether GT or Forza have been at the forefront of realism racing anyhow.

He probably meant crash damage and handling.  Which I believe is true, to each his own I guess.

We haven't really received any info, past speculation and vague rumors.
I'm sure we'll have more info come E3, but you can't compare until that time.

Past that, I somewhat agree on the lack of collision modeling (Comparison to MarioKart is amusing at best), but to be fair, GT5: Prologue is not GT5.

Yeah the mario kart thing was jokes. :) But on the whole prologue thing. Dont expect much different. aside from full trcks list and car list, and added online elements the game will visually and play almost identical.

GT4P is exactly the same game as GT4 except for ALL the content. Dont expect a radically different game. Just the same game but complete. :)

Thats why I'm very confident I can play GT5P and know what I'm getting with GT5.

Correct me if I'm wrong, but wasn't collision modeling confirmed for GT5?
That alone would radically change the experience.

We still have to hear details, though I'm fairly confident in saying there will be something new on the disc besides the basic new content (Cars, tracks, etc).
Either way, it'll be interesting to to see, the game has been in development for a long time now.

They originally announced they'd be adding collision damage to GT5P via an update.

 They said they were looking into it. It was gonna be an update to trial it with GT5P but that never happened. Problem is they would have to remodel the cars with individual parts instead of just modelling the car as a whole. damage modeling can add loads of dev time to each car model. All the time spent remodelling each car would be awhile. If damage is to be in GT5 I would expect a xmas 2010 release. If it's not then I expect xmas 2009, Feb 2010.

If they had modelled the cars with every individual part to begin with (bent parts crumpled parts etc etc) they would have it ready. But they didnt. And I cant see Polyphony changing their past ways and make GT5 radically different from GT5P. No previous Prologue has been barely different at all.

Hmm, I guess we'll have to see then.
Although a Fall/Christmas 2010 release does sound plausible, unfortunately, so I wouldn't be surprised to see it included.