If you need more than 4G of memory (ie. if you think it's probable that swap is going to get used), using 8G + HDD is a no-brainer. SSD is a fantastic improveme

If you need more than 4G of memory (ie. if you think it's probable that swap is going to get used), using 8G + HDD is a no-brainer. SSD is a fantastic improvement over HDD, but the difference between memory -> disk is not a factor of few (like HDD->SDD), it's orders of magnitude.