Try your transceiver module first if you're not sure if it's compatible with your host equipment. Keep in mind that compatibility has nothing to do with the functions of the transceiver, but in recognizing ID code.
Both SFP and GBIC pioneered manufacturer coding within the transceiver. The coding was designed for network management software to be able to log the pluggable modules within the network. However, Cisco and other manufacturers used the coding system to discriminate third party transceivers except those that had the same host equipment's ID code. This forces you to use only Cisco products, but not anymore. Transceiver manufacturers have developed modules that are Cisco SFP compatible, for example.
As an added feature, SFP modules have Digital Diagnostics but not all SFPs have DD. Only the higher end SFPs used for extra ordeal or for CWDM have DD. It permits the host equipment to read report details such as actual received optical signal level, output power, and the temperature within the SFP module.
When picking a transceiver module, be cautious about a couple of things to ensure it is compatible with your existing host equipment: (1) Does the SFP require DD functions? (2) Does the host equipment check the ID code and lock out third party modules? So, to make sure that your transceiver module doesn't go to waste, try it with your host equipment and see if it doesn't reject it.
If you possess a three-year old or more Cisco equipment, chances are your non-Cisco module will be discriminated. On the other hand, newer Cisco equipment no longer has this feature, probably due to complaints and pressure to stop monopolizing the market. That leaves you two options: either you buy new Cisco equipment to be able to use cheaper Cisco GBIC compatible transceiver or keep your old Cisco equipment and bear with using more expensive Cisco transceivers. The choice is yours.
Keep in mind that compatibility has nothing to do with the functions of the transceiver, therefore the brand doesn't really matter. What's important is whether your host equipment requires DD function and does it lock out third party transceivers or not.