Guinea pig or a rat? need help.?

well i decided to buy a new pet after my one and only fish dies. or maybe just buy it anyways this summer. i wanted a big pet but either rat or pig will do but are rats active during the day because i know rats to be nocturnal animals. And how about pigs? Also which one seriously needs a playmate for when im not around to play and snuggle with? and which is most human friendly and would love to be held and played with someone told me pigs just sit on your lap is this true or they run around like crazy too?