Yes, I 100%'d the Wii version and the Xbox 360 versions when they came out. I haven't played the Wii version since, but I still remember much about it.
In general, I think it's the inferior version. It's still a good game, but the world building/side mission aspect is completely gone in favour of hub worlds that are just static screens, and much of the charm the NPCs had is lost because of this. This version of the hub worlds just pads the game out in my opinion. People argue the same about the HD versions hub worlds, but I disagree with that assertion due to the fact the world and NPC characters are so fleshed out, making it feel like Sonic Team put legitimate care, effort, and passion into those sections of the HD version. Here, the hub worlds just sort of get in the way.
The Werehog gameplay is also MUCH worse in the Wii version. It's not the worst thing in the world, but it's very mediocre. While the HD version's Werehog gameplay felt like a family friendly God of War clone (while still retaining the same level of general complexity in level design and fighting mechanics), the Wii version Werehog gameplay feels like an average licensed tie-in action game for a kids movie. The level design is generally much more simplistic than the HD version, with some very basic platforming. Sonic also just doesn't feel very fluid, he's incredible stiff, especially when swinging across poles and what not (whereas those kind of actions have actual physics applied to them in the HD version, making them feel more fluid and your options are more dynamic). The combat is also just really simple. You alternate between pressing the L and R shoulder buttons to complete a full combo, and that's pretty much it. You get a couple of new moves over the course of the game, but they don't add much and really just replace your old moves. The levels are generally much more linear here as well. On the plus side, I think the Wii version's Werehog levels do have a little more environmental variety. Even within the same continent, the Werehog levels play around with different environments. For example, in Adabat, there is a level that takes place in the town as you would expect. But the next one would be taking place on small, wild islands in the sea, with giant whirlpools to make your way across. Then the next one could be in the tree tops, and so on. Also yeah, the Werehog levels are split into 3, 4, or 5 mandatory levels (depending on the continent). They're shorter than the HD version's Werehog levels individually, but longer when put together. Overall, I actually quite like the HD version's Werehog levels, and find the Wii version's Werehog levels disappointing by comparison.
The regular Sonic gameplay is still the star of the show here. It's not as fun as the HD version's in my opinion, but they're still quite solid. For the most part, they're the same general idea. The only major difference is how the boost is handled - in the HD version, holding the boost button allowed you to continually consume your Ring Energy in order to boost. In the Wii version, however, the boost gauge is segmented. This means that instead of holding the boost button down to continually boost, you press it once, it depletes one segment of your boost gauge, and then Sonic rockets off for a few seconds before returning to normal speed. This changes the dynamic of how the boost is used - instead of trying to maintain one, continued boost for as long as possible, you are trying to chain multiple boosts together to keep the flow going, using them precisely at the most optimal times. I prefer the HD version's boost mechanic myself, but I still find the Wii version's system fun and engaging in it's own right. You might even prefer it if you found the HD version TOO fast, as the Wii version's level design doesn't expect you to use the boost as much. The level design is also a bit more barren in the Wii version's day stages, but it's not a huge deal breaker and it's normally populated enough to keep things interesting. Other than that, if you liked the day stages in the HD version, you will probably still like them in the Wii version, as it's pretty similar.
Also Sun and Moon Medals are handled completely differently - instead of being found in the world, they are awarded to you based on stage ranking. They are also not needed for mandatory progression. Instead, the unlock optional puzzle rooms in the Gaia Gate hubs (basically just your entrance to the levels, they're like Warp Rooms from a Crash Bandicoot game), which house various hidden items like concept art, music, videos, and even secret missions. These puzzle rooms are actually my favourite aspect of the Wii version, and are wholly absent from the HD version. Within them, you tackle short platforming-puzzle challenges by switching between Sonic's regular form and Werehog form on the fly. They aren't too terribly difficult but they're fun to do and just an interesting implementation of the Werehog form, and do get more complex as they go along. Plus the music is
incredibly soothing. Here's a video example of them.