A table saw is more precise and makes cleaner cuts. This is very important if your projects require joinery. You can also make dados with an optional dado set. A portable circular saw is, well, portable but you are pretty much limited to making straight cuts and it is very imprecise and is generally used for rough cuts where variations of up to 1/8" is inconsequential. Decide which you need, and buy a high quality tool. Cheap tools render cheap results.