Actually both are 2000 DPI.
Between the two I would personally say the Logitech wins for several reasons. Better teflon feet, a more ergonomic and comfortable layout (This is of course more of a personal choice), the ability to add weights to make the mouse lighter or heavier for whichever type of mouse you prefer, and better overall software plus hardware on the fly switching (Does not have to have software installed to do the on the fly sensitivity switching, or at least that is what I have read. I understand with the Razor you do have to have the software installed for the switching. This is not a huge thing, but say if you use Linux and such you can do the on the fly switching with the Logitech even without the software, which is a nice plus if you prefer to not install their software).
The Copperhead does have better button placement, at least in a way, than the Diamondback did. They are lower and back a little bit. Being lower they are easier to find and click than they were on the Diamondback but being back some annoys some people.
But bottom line over all of this comes down to this, at least imo, the price. The Logitech G5 is quite a bit cheaper.
Ok I notice you say in your post the G7 vs the Copperhead. I think you mean the G5 vs the Copperhead. The G7 is the wireless version of the G5 so not really a fair comparison as they are different types of mice. If you are wanting wireless then there is definatly no competition as there is no wireless Razer. But the G5 is the direct competitor to the Razer Copperhead. Like I stated, both are 2000 DPI but the G5 just has alot more features that are better overall imo. The ability to add weight to the mouse, the huge teflon feet, the hardware sensitivity switching, and the much lower price make the G5 the clear winner in my book. The one advantage the Copperhead has imo is its alot smaller, so if you have very small hands then it may be better for you.
Whatever you decide though I am sure any of them would make a great mouse. So good luck friend.
Edit: And on the above note of the Diamondback or the 518, if you decide to go with a lower priced one also check the
Optorite Laser Mouse. Its cheaper than all of them and its a true laser with great teflon feet, lots of buttons, a very nice ergonomic layout, especially for someone with medium to larger hands and only $22 from Newegg. But that is if your wanting to consider a cheaper one. I have heard from quite a few people who have the Mx518 or the Diamondback and prefer this mouse over both of them. I just ordered one myself so when it arrives I will let you know how it feels. I wanted to go with the Red as it looks really nice, but I have a Blue and black case and am ordering the Blue and black Saitek keyboard so I went with the blue just to match the rest of my system. But good luck again with your choice.