do you plan on only running 4s? or might you step up to 5s or 6s in the future. If you know you will only ever run 4s then get the 1515 1.5d, if you might run 5s or 6s in the future look at the 1515 1y. I have not run and MGM controller yet, but from what i've read here and a few people that i know that run them it will be my choice for my e-revo unless the MMM makes it out in the next month.