Put the catalog on the SSD (drive 2, not system, preferably), and keep it there.
If you want to and got some spare room, you can try to import your images on the SSD, and then, move them (from within LR of course!) to the HDD when you're done editing and processing.
As the others, I wouldnt wait for much a difference between the 2, but you can try for yourself.
And don't use multiple catalogs until you got a real good reason to (ie content you do not want to mix at any cost - eg kids portraiture as Dr Jekyll's daywork and lingerie as Mr Hyde's extra
, or work for clients that are competing each other...).