I'd definitely get an original Sony cover again. The cover with light is a bit different, it weights more, and the spine is different. I like the spine of the cover without light more to tell the truth. But the cover without light has other disadvantages, for example: It doesn't have light.
In Europe you can get the cover without light for 20 Euros in some stores, have a look at Ebay. Maybe you can save a bit.
You can keep your old cover and use it for outdoor use or for a vacation. I have serveral Sony covers now, some are not that nice anymore, but that's normal if you use your Reader on a daily basis, I think.