[Patrick]

I think glassdoctor might have used both those motors on 4s for racing in one of his buggies. I think he got a bit better runtime from the 1512, but that was a buggy and I don't know if it would be different for a truggy since it might need more torque.
The 1700kv 1515 is ok on 4s, but you have to gear up a fair bit to get any decent speed and it looses a bit of much. Don't know what it's going in, but I'd choose a bit more kv for 4s.