Every transceiver today comes compatible with both fiber optics and copper wiring, but they also are accessible to the Ethernet standards your business may use, such as 10GE and 100GE as well as earlier editions such as gigabit Ethernet. If you end up ordering a module, just make sure it supports the newer standards, because as time passes by, your older 10GE may not be the norm and you may need to invest additional money just to obtain faster speeds. When ordering an older module, it is wise to get a product that can still support the newer standards that may make their way to the market, as times will continue to phase out the older standards to make room for the latest ones. You might be interested in Cisco GLC-T transceivers that support all the past and new standards that look to be making their way to the industry.
Please note: a warranty will save you a ton of money if the day ever comes when your module breaks and you need to replace it or get a particular part fixed. Cisco and Dell build trusted items for shoppers, but these modules often go through the wear-and-tear of daily use that can cause them to lose their effectiveness over time. Sure, you may end up shelling out a bit more just to get the warranty with your item, but what's worse is being without one when the product breaks.
Everyone has a price range they would like to spend on a product, and the higher the cost, the more features will be included, but just be certain you actually intend to use the added perks to not let your money go to waste. When ordering new SFP transceiver modules, always make sure the price looks reasonably close to those of competitors so that you wind up with the best deal.