I've been asked to post my thoughts in this thread instead of making a new one.
So here it goes.
First, let me start off by saying I own both games. Purchased GT5 on launch and purchased Forza 4 yesterday.
I went into both games with an open mind. I have owned/played the following racing tittles on console
Gran Turismo
Gran Turismo 2
Gran Turismo 3 A-spec
Gran Turismo 4
(rented Gran Turismo Prolouge)
Gran Turismo 5
Collin Mcrea rally 2.0
Forza 2
Forza 3 (borrowed)
Forza 4
Need For Speed Shift 1
Need For Speed Shift 2
Need For Speed HP
Dirt 1 and 2
Grid
With that stated please realize I am in no way biased towards a single game, I just play the games and enjoy them for what they are or at least try.
As far as comparing the two racing games, GT5 vs Forza 4, I have to give GT5 the lead still as far as driving and racing goes.
Physics:
In my opinion, compared to GT5, the vehicles in Forza 4 almost seem to float on the track. at no point in the game do I really feel that I am on the road, but just above it, this for me is most prominent while coming into a corner, even at low speeds I get massive under steer from any car. I have yet in Forza to experience over steer even when I tune my car to make it happen. Whilst with GT5 when I come into a corner I feel a connection with the pavement when I brake into a turn, sure, Forza 4 shows more body roll I've noticed when coming into the turn but to me its all flash/looks. I still feel like I am floating into the corner, brakes lock up at the drop of a hat and its off into the grass I go. Some raise an argument saying maybe i just stink at playing the game.. I may not be the best in the world, far from it. but I look at myself as above average. I know they are two Different games with two totally different physics engines, I just feel GT5/PD nailed it better than T10/F4 did. Racing to me is all about mastering the corners, anyone can go straight and fast in a game and even in real life. But coming into a sweeping turn at 30mph while off the brake and the accelerator coming in high attempting to come in towards the middle only to find myself going even more high and into the grass/dirt is just strange to me when I see no reason for the vehicle to be doing so. Speaking of grass and dirt, why is it that Forza still thinks that grass and dirt are rubber magnets and will slow your car down to a near stop from 100mph, is it just the devs team way of stopping corner cutting? I've noticed that some areas act correctly when it comes to grass while some just STOP your vehicle outright almost, it shouldnt take me 10 seconds to get out of gravel/sand 10 feet away from the track with an awd evo. Now onto one more thing with the physics, Drifting. In gt5 its still pretty tough to drift with any car other than a RWD or a drifting tuned AWD car, with Forza 4, it seems that any car off the lot is a drifting machine, be it a FWD compact hatchback or AWD road hugging monster, oh yeah, and no rallys in Forza 4, boooo
AI:
Both games have a their plus and minus here I believe. GT5 having a more robotic AI that sticks to a set path on the course and does not even notice you're in the game or pose any real challenge with you unless you stick with the classes/specs of the other racers. While Forza 4 the AI seems a bit more alive and battles even with itself. On the other hand though, the AI in Forza 4 feels like its on rails and they are driving in tanks. I don't purposely go out of my way and try to hit the other cars, I try as hard as I can to race clean. but accidents/rubbing/collisions happen, and when they do happen in Forza, OH MAN. Brake into a corner early and get rear ended by the AI, you're pretty much doing a 180 and sitting in the dirt while the AI goes on its way like nothing happened, yet at the same time, go into a turn following the AI and brake late and rear end them, the same thing happens, you end up getting dizzy and losing control while the AI still goes on its way jamming to the techno music like nothing happened. not to mention the AI loving to pit maneuver you whenever it has the chance. It just feels like no matter what cars are on the track, they are glued and weigh 10x more than they should.
Customization:
Forza 4 wins in this category hands down. I love sitting in the garage painting my cars and doing all sorts of stuff with them, its fun. Maybe someday PD/GT5 will get the hint and let this level of detail with paints/decals find its way into their product.
Graphics:
Many will argue "well, GT5 may have 1000+ cars, but only 200 are premium and look any good" while this is true, the 200 premiums look better than anything that is in Forza 4, every single detail and every single inch of the car is covered in the premiums. Forza 4 in my opinion is too glossy, every car has a wet shine to it that's over the top, the colors are too bright, not only on the cars but on the track, from the burms, to the tarmac, to the grass to the background grand stands and tents. It just seems more like a cartoon than real life. again, that's just how I see it, everyone see's things they way THEY see them. Now, damage, Forza wins, yes, sure, but one thing that needs to be understood was that PD was not allowed to put damage or show damage in the vehicles in past versions because of vehicle licensing issues, forza was given the go ahead from their first game. I'm going to give PD the benefit of the doubt on this one and say they will get a better damage model in a future game. damage DOES play into realism i think, mechanical damage for sure, if i whack a wall at 60 mph I should know I did for the rest of the race. T10 pretty much has that down for the most part, I say give PD time. I believe they put more time into the physics and dynamic weather engine then worked on adding some damage.
Forgot shadows too, ive noticed some shadow issues in both games to be honest, one main one is GT5 jaggy shadows, we all know this. But in forza one thing ive noticed with shadows is when in cockpit view with head tracking and looking around, if you look at your shadow outside, the trunk and hood are gone and its just the cockpit/cabin portion of the car visible as a shadow.
Online:
I cant really comment on this one yet, I'm still working on my single player with Forza 4 and not really going online, I need to get the handling down before I go on there and give a fair review of the two. The only thing I will say is, The two times I did go online with Forza 4, it took a very long time to refresh and load/connect to lobbys and rooms. I did love Froza 2 online though, So maybe I'll come back and update what I think of online, if people seem to care. haha.
There are of course a lot more things to debate in each category I'm sure, but these are just things that stand out to me the most, and well.. this is already a TLTR post almost.
Overall as far as console racing games go my ratings would have to be: *keep in mind this is based on whats on console, not PC*
Graphics: GT5 9/10 : F4 8/10
Physics: GT5 10/10 :F4 7/10
AI: GT5 7/10 :F4 7/10
Customization GT5 5/10 : F4 10/10
Online GT5 7/10 : F4 TBD
Over all: GT5 9/10 F4 7.5/10 (keep in mind this overall score is based on racing experience, some may argue "but you gave forza 10/10 for customization", sadly, these games are not car painting games, they are racing)
Hope this review/opinion was better than my previous thread. I wrote it in a hurry and was venting.
Take care.
Steve