I've used both. I had an MX518 for ~ 2 years (2005 - 2007) and it was pretty darn good. Still in use on another system for general work and despite the abuse it has suffered, it just keeps going on and on.
It's only problem was that if I alt-tabbed out of a game and back again, the custom bindings to the side buttons wouldn't work. I think that was a software/driver issue; the mouse customization software was itself a bit buggy and some settings wouldn't stick. Those issues may have been fixed by now.
Since 2007 I've been using the Deathadder and performance-wise it's better than the MX. It's more comfortable to hold, feels lighter (don't know if it actually is, though lol), easier to move around, and the Razer customization utility is top-notch. You can customize profiles (upto 5) easily with individual sensitivity. dpi, and keybinding settings. I've assigned macros to the side buttons for general usage profiles- very useful.
The deathadder's main drawbacks are its relatively poor build quality (my first one quit after 1 year or so) and the lack of a on-the-fly sensitivity changer switch. It has a profiles switch at the bottom which is pretty much useless in-game.
All pros and cons considered, I'd pick the deathadder for its better feel, performance and customizability, if you can live with its possibly premature demise under heavy usage
It's only problem was that if I alt-tabbed out of a game and back again, the custom bindings to the side buttons wouldn't work. I think that was a software/driver issue; the mouse customization software was itself a bit buggy and some settings wouldn't stick. Those issues may have been fixed by now.
Since 2007 I've been using the Deathadder and performance-wise it's better than the MX. It's more comfortable to hold, feels lighter (don't know if it actually is, though lol), easier to move around, and the Razer customization utility is top-notch. You can customize profiles (upto 5) easily with individual sensitivity. dpi, and keybinding settings. I've assigned macros to the side buttons for general usage profiles- very useful.
The deathadder's main drawbacks are its relatively poor build quality (my first one quit after 1 year or so) and the lack of a on-the-fly sensitivity changer switch. It has a profiles switch at the bottom which is pretty much useless in-game.
All pros and cons considered, I'd pick the deathadder for its better feel, performance and customizability, if you can live with its possibly premature demise under heavy usage