The answer to your questions is it depends on the size/capacity of the ssd you are going to buy. Are you thinking 32GB, 64GB, 120GB, or something larger? What will you be doing with your computer?
Intel's Smart Response Technology (ssd caching) was originally designed for use with a small 10GB or 20GB solid state drive and a hard disk drive. Microsoft Windows and all software applications are stored on a hard disk drive. The small ssd is used as a cache for the hard drive. The result is a small increase in hard drive performance. Unfortunately using a small ssd as a cache for the hard drive does not utilize the ssd's full potential. The performance increase is not as good as storing Windows and software applications on a larger capacity ssd.