I use Ensembl whenever I can. I like that they have an internally consistent system of IDs and they have "releases", so if you pick one (I think 114 is current) and stick to it, everything should be compatible. Note that the "main" mouse genome (GRCm38/39, mm38/39) is based on the C57BL/6 strain. I think the most basic genes should be similar in all mouse strains, so you can get away with using that, but if you have a different strain and want to be "accurate", you would have to find an alternate genome assembly and the matching gene annotation (GTF). I have never done that, though, so I have no special advice for that. Ensembl might have such files, but I have not looked.