Hun, it depends what system you are working with, as it's always better to use the correct lamp for the appropriate system.
If you don't, even if your gels might look cured, you can't be 100% guaranteed that they indeed are.
So if you work with cnd, take the cnd. If you work with gelish, take the 18g gelish etc.
What brand do you mostly work with? Since you are working with many, I suggest take the lamp whose system you use the most. Do not buy a generic lamp, since it won't work properly with any of your systems.
I have the CND Led Lamp by the way and work with Shellac and absolutely love it. Best purchase I ever made. and Gelish works fine with it from what i'm hearing. can't say for other brands