Communicating from PICAXE M2 series to Arduino UNO advice needed.

I would like to have a Picaxe driven sensor on one board and have it pass data to an Arduino UNO (or Mini or Mega). I was wondering what the best (easiest) way to do this was. for instance I would like to pass analog values and digital like from a temp and motion sensor. Should I use something like i2c? or serout? Any ideas would be appreciated. Thanks