Custom Google Search vs Global Site Search?

Hi There. I have website running on WPMU 3.5 and some custom post types included (built with CustomPress). To improve my global search on the website - so give to visitor the best experience in searching through posts AND custom posts types present - should I use plugin "Custom Google Search" or "Global Site Search"? As I can see both should produce the same results. I kind of lean to Google as I expect it will provide better results with less resources. Can you please give me PROS and CONS and let me know what is your recommendation?