Tbh idk besides LOTS of use, I really and honestly have bough A LOT of logitech headset mice and keyboards and I still love their stuff more than most any other brand you can find at Radio Shack / Wal-Mart but they always seem to break on my within a few months, so much so that I started buying the insurance packages so I could replace them cheaper. Also their wireless royally frustrates me, loses connection on and off from 6 inches away because it goes through half and inch of particle board....
I was going to get both of those before I got my Naga and Lycosa but simply put the screens were rather useless (Especially if you have 2 screens already) and the ergonomics of both were really not that satisfying at all. In fact I liked several of their other non gaming additions key boards much better.
The Nostromo is imo much better than the G13 especially for comfort, but also for its really good macro and profile programs.
As for people saying Razer is more expensive to gain less. I have checked the main competitors. Steel Series, Logitech, Razor ect and Razor is typically the cheapest and imo most well thought out as far as button positioning is concerned. Steel Series was the most expensive with the least features and worst reviews.
If you are gonna get anything Razer do it from Amazon.com they have everything cheaper by about 10-15 bucks.