How to know which ortholog database is the best for my work?
To recover orthologous sequence for model species
You should be able to find your orthologs using BioMart and your gene IDs.
There are numerous way to do it, directly on the ensembl website or through API. You can start from these links (quite old though) :

http://www.ensembl.info/2009/01/21/how-to-get-all-the-orthologous-genes-between-two-species/
https://www.youtube.com/watch?v=EwfOQsr2O-M #Get orthologs via BioMart
https://www.biostars.org/p/12245/ #Finding Human/Yeast Orthologs Using Embl?

Which database should I use
It is broad and depends on the nature of your work. In your case, working with &quot;major model species&quot;, DIOPT (the first line of the table in Quest For Orthology) has the very feature you need on its front page for going from mouse to human. More eukaryotic/viral oriented database will be used for taxonomic identification, annotation inference, etc.
I hope it helps.