If you are new to mask making in general (don´t know if you´re also new to sculpting and modling/casting) I would suggest to start with a latex mask better.
Silicone masks imply more advanced molding and casting skills (mold with a core, laminating, degassing (if possible), injection etc. and sculpting of course)). It´s an expensive material and process. Starting with this can be frustrating and expensive, latex will be easier and cheaper to start with.
If you have these skills, forget what I said and go for it!