This review has comparisons between both versions.
First off, I've played through both the PS3 and Wii versions of the game, and this review will be written in terms of the PS3 version unless stated otherwise.
This game brought a lot of of Sonic game play ideas, but it tried something new at the same time. The main idea of the story is that Sonic has to restore the power of the Chaos Emeralds, and in turn, repair the planet, which was separated into 7 chunks of planet that kind of float off of the core, but for some reason never quite float away into space. I assume this is because of the gravity of the core or something, but I'm getting off track here. The story isn't vital to the game at all. It does however feel like a cartoon more than anything during the majority of it.
The main game play is split into 2 parts, and in the Ps3 version, you will have 2 levels of a 3rd game play type that isn't featured in the Wii version. The first being regular Sonic. He is all about speed and finding the most effective short cuts through the stage. Then there's the Werehog. It plays a lot like an odd Streets of Rage kind of thing. Then there is the 2 levels of piloting the Tornado and pressing on screen commands to shoot down matching enemies.
The Sonic levels work great. It's the first time in a long time where you will actually get a sense that Sonic may actually be the fastest thing alive. You can upgrade Sonic's speed with experience points you get from destroying enemies. The speed will be maxed out at level 11 and you can upgrade the ring energy up to 6. These will both greatly effect how much faster he will be able to move, how long his ring energy will last when being used, and how much each ring will give to his energy meter. The ring energy is used to do a boost which makes Sonic run even faster, and allows him to just plow through enemies instead of being hurt or stopped by them.
The Wii version is significantly different. First, the stats cant be permanently upgraded since experience points dont exist in that version. The boost gauge is filled by collecting rings, and this affects your max speed. the more rings you have, the faster you are allowed to move. Also when boosting, it will only last for one section of the ring energy meter and then you just go back to normal speed. In the PS3 version you can boost constantly until you run out of ring energy.
The day time levels looks pretty good. There's nothing amazing here, but you move so fast that a lot of time you wont really be paying attention to scenery anyway. The night time levels look less detailed, and a lot of the areas look the same through the entire level.
The Werehog is where this game might break the deal for you. This is one of the more random ideas they have thrown into the games in recent years. Basically you give up speed to be a big, bulky, slow, powerhouse. There are around 30 or 31 combos to use as the Werehog. He is able to run, but not as fast as you would want him to. He has the ability to stretch his arms for some reason, so this is involved in most of the combat. You can upgrade everything in this form from health and unleashed meter to strength and shield. The Unleashed meter works like the Devil Trigger in Devil May Cry, but the unleashed meter doesn't heal you. There is also a system where if you beat an enemy to less than half health, they will have the circle button displayed over them. If you press it, you go into a button sequence. If you press everything correctly, they will die no matter how much health was left, and will give more experience points. If you mess up this sequence, they regain health and attack you without letting you block or avoid it.
The Wii version has only 5 levels to each upgrade, and only 3 stats to upgrade. There are no experience points, so you gather Dark Gaia energy instead. Once you get so much, you get a preset upgrade. You are never free to chose what improves or when. The shield is unlimited in the Wii version, but in the PS3 version it has a set power level than will deplete with damage to it, and can be restored.
Exclusive to the PS3/360 version is a Tornado mini game with 2 acts. One is early on in the game, while the other is when you try to get to the 7th continent. The stages are just a level where you have to press a button that shows up under an enemy to shoot them down. The plane moves on a rail so you cant actually control anything other than if it shoots or not. Its nothing special, but it is kind of fun for a break form the action.
Most of the game deals with exploring each continent and trying to find the temple there to restore the emeralds. The continent phases are extremely different in each version. In the PS3 version, you get to run around the towns and talk to everyone, do missions, and buy stuff at the shops. In the Wii version, you get a screen with icons to click. Both versions require Sun and Moon medals to unlock stages. The Wii version just hands the medals over to you at the end of stages. You can get up to 3 in most stages. The PS3 version makes you hunt them down. There are random amounts of each medal in each stage. The Wii version doesn't require any real number for the main stages, but the PS3 version does. This gets kind of annoying when you need a large amount to just progress in the main story, but you don't know where the missing medals are located. In all, there are 200 of each medal in the PS3 version, and I'm not positive how many are in the Wii version.
The PS3 version also has a few levels not in the Wii version. One continent in the Wii version is just a boss fight and the picture with icons, while the PS3 version has the full set of levels.
Overall, this game isn't bad to me, but there are a few things that really weren't needed at all. This game gave us a Sonic game about Sonic, which was a very welcome change. For the first time in years, we got a Sonic game where we didn't have stop the action to hunt the Master Emerald, use teamwork, be an emo hedgehog, or anything else that takes away form the fun. The werehog is something that you either like or you hate. I ended up liking it, and some other people will too. I recommend renting this game first just cause the downloadable demo doesn't let you play a night stage. If you are an old school Sonic fan, and can put up with the werehog, you will probably love this game. Also people complain way too much about the Sonic stages being too fast. If you have slow eyes and bad reaction times, don't blame the game for your own problems. It's a Sonic game. If you don't like speed, don't play the Sonic games. Its that simple.