In a buggy, Large Motor (1515) or Small Motor (1512)?

In a few days my Losi 8ight 2.0 buggy will arrive and I'm trying to decide what I want to run for a motor. In my Truggy and Monster truck I've been running 1515/1y motors. To be honest I'm fairly certain that I'll either just run one of those in the buggy (because running 3 classes is a bit insane) but I wonder what you guys who have run buggies have to say. Is a "big" motor like the 1515 too much for a light 1/8th buggy? What would the benefit of moving to a 1512 be? Is the weight difference that much of an issue (about 70 grams)?

Thanks for any input you guys have.