The only problem I see with using the plate method is how enormous some plates are. It can be easy to overfill the plate, especially if (like me) you just got new plates that are 50% bigger than the old ones. It won't hurt to measure and count for a few weeks until you get a good idea of what the portion sizes look like. After that, measure it out every now and then to be sure to aren't creeping one way or the other and you will probably be fine.
Anastas Dimitar Martin