So unable to decide on which mouse, I just bought a bunch.
Here's a quick review on everything. PS. I'm going to try and avoid specs, battery life etc.. those are easy to find. I'm going to focus more on use and feel:
My baseline: Wired Mighty mouse. Good for what it was, but not great. A little slow on the tracking even when maxed. And as everyone knows the ball needs constant cleaning. I'm pretty sure everyone knows this mouse.
Bluetooth Mighty: Never was happy with it. The tracking always seemed jerky (and it was slow). Found out later its due to the laser (less dpi for tracking) likely to increase battery life. Same issues with the ball.
Logitech: Performance MX: Wireless mouse using a usb transceiver. The build is great, comes with great packaging and accessories for the price. The mouse is nice, and features are good if thats what your into. Over all use is really good. The forward and back buttons are surprising useful, as is the thumb button (use for expose). The wheel is okay: not a huge fan of the smooth scroll at low speeds (good when moving fast), nor the clicks at high speed (good when moving slow). To bad they didn't keep the automatic smooth scroll at high speed like the MX Revolution. I also don't like the button behind the wheel, it's the best spot for it, but I don't like the the feel of it when using the scroll wheel. And the left and right joystick/scroll (on the thumb wheel) is hard to use, especially pushing right due (due to the curve of the mouse and less wheel to grab). As for tracking, the mouse is quite precise (but not the best). The big thing for me is weight and feel (to heavy for my tastes, but some like weight so this could be a positive for you) and my thumb doesn't quite fit in the groove right.
It's worth noting, that this mouse is designed to fit your whole hand, and let it rest on the mouse. As a result it's taller and but more you're weight onto the mouse making it feel heavier. It's still comfortable, and no worse than a Magic, just different. Overall quite good. Verdict: Read the reviews, and see the specs, read about the features, you should know what it is. If you like weight, don't mind the look (being black in colour and so large it looks dominating) and it feels good to you, than it's probably right for you. It's a solid mouse, no if's and's or but's about it. Comes down to preference. It's on the other end of the spectrum to the Magic.
Magic Mouse: First up, if I'm using MagicPrefs. Without magicprefs (mp) I would choose the Logitech MX. I used the mighty's centre button expose all the time (which thanks to mp's I can on the Magic). And the system max speed is to slow for me (would bug me), but fixable with mp. I'm also using some three finger swipe stuff (but thats just bonus). Magic preference really does make the mouse, changes it from good to great. As for looks, I personally prefer a smaller looking mouse that matches (desk looks less cluttered). But more important is how it works. The inertia scrolling is great, and just like my trackpad. Gestures (with mp) is great. Tracking is great, super smooth and precise, probably the best I've ever used. The magic also slides nicer on my smooth wood ikea desk. It's just smoother to move, hard to describe. The MX is better than most in this regard (including the mighty), but the magic is even better, which I really like. The weight is nice and the feel is good, but I'm used to my Might mouse. I like a mouse I can hold with my thumb and ring finger. If you like to rest your hand on the mouse, than something like the MX would be better for you. The magic just feels right to me, and isn't painful at all. If anything it could be hair wider at the base (closer to the mighty in width). I should also mention I don't over grip the mouse (which could cause pain), I use a relaxed light grip which is very comfortable for me, and I rest my had on the desk. Verdict, thanks to MagicPrefs is a solid mouse and great to use. It's more light and agile than the MX, both visibly and in use.
Both mice are great to use, and both can stand their ground. I think it comes down to what you prefer in terms of weight, looks and grip. If you don't like one, you'll probably like the other. If one style of mouse appeals to you for look, feel, or weight, then get it. Both are solid choices.
Final verdict for me:
Not sure 100% sure yet, but I'm strongly leaning towards the Magic. I prefer the looks, weight and gesturing. Both mice are comfortable, but in terms of size neither is a perfect fit (mice are cookie cutter, not custom built). For comfort, they're different. The MX is more comfortable to hold, but the apple is more comfortable to use.
I'm going to keep using both for a few days, and keep my favourite. Current leader is the magic mouse.
PS. If I keep the Apple, I'll get the Mobee wireless charger (as it chews batteries). Which means both mice are the same price in the end (within 5 cents!).